Transfer material used for producing a wiring substrate

ABSTRACT

A transfer material capable of transferring a fine wiring pattern to a substrate reliably and easily. The transfer material includes at least three layers of a first metal layer as a carrier, a second metal layer that is transferred to the substrate as a wiring pattern, and a peel layer adhering the first and second metal layers releasably. On the surface portion of the first metal layer, a concave and convex portion corresponding to the wiring pattern is formed, and the peel layer and the second metal layer are formed on a region of the convex portions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 10/283,386 filed Oct. 29, 2002, which is the continuingapplication of U.S. patent application Ser. No. 09/778,709 filed Feb. 7,2001, and which applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a transfer material for transferring afine wiring pattern or circuit components to a substrate, and a methodfor producing the same. Furthermore, the present invention relates to awiring substrate on which a wiring pattern or a circuit component isformed and a method for producing the same.

2. Related Background Art

Recently, with a demand for high performance and miniaturization ofelectronic equipment, high-density and high-performance semiconductordevices increasingly have been desired. This leads to a demand for asmall size and high density circuit substrate on which suchsemiconductor devices are to be mounted.

In order to meet such demands, a connection method using inner via holes(IVHs) that can connect between wiring patterns of large-scaleintegrated circuits (LSIs) or circuit components in the shortestdistance has been developed in various fields. In general, an example ofwiring patterns having such IVH configurations includes a multi-layeredceramic wiring substrate, a multi-layered wiring substrate produced by abuild-up method, a multi-layered composite wiring substrate including amixture of a resin and an inorganic filler, and the like.

The multi-layered ceramic wiring substrate can be produced, for example,by a following method. First, a plurality of green sheets including aceramic powder such as alumina, etc., an organic binder and aplasticizer are prepared. Then, each of the green sheets is providedwith via holes and the via holes are filled with a conductive paste.Thereafter, a wiring pattern is printed on the green sheets, and theprinted green sheets are laminated. Then, the thus obtained laminate issubjected to a binder removing treatment and a firing treatment, thusforming a multi-layered ceramic wiring substrate. Since the thusobtained multi-layered ceramic wiring substrate has an IVH structure, anextremely high-density wiring pattern can be formed. Therefore, suchmulti-layered ceramic wiring substrates are suitable for miniaturizationof electronic equipment.

Also, the print wiring substrate produced by the build-up method, whichimitates the structure of the multi-layered ceramic wiring substrate,has been developed in various fields. For example, JP9 (1997)-116267A,JP9 (1997)-51168A, etc. disclose a conventional general build-up method.In this method, a conventionally used glass-epoxy substrate is used as acore and a photosensitive insulating layer is formed on the surface ofthe substrate. The surface is provided with via holes byphotolithography, the entire surface is copper-plated, and then thecopper-plated surface is subjected to a chemical etching process, tothus form a wiring pattern.

Furthermore, JP9 (1997)-326562A discloses a method in which a conductivepaste is filled in via holes processed by photolithography as in thebuild-up method. JP9 (1997)-36551A, JP10 (1998)-51139A, etc. disclose amethod for producing a multi-layered substrate by forming a conductivecircuit on one surface of a hard insulating base material and anadhesive layer on another, respectively; providing through holesthereon; filling the through holes with a conductive paste; and thenlaminating a plurality of base materials to thus form a multi-layeredsubstrate.

Furthermore, specification of Japanese Patent Nos. 2601128, 2603053,2587596 disclose a method for producing a multi-layered structure inwhich an aramid-epoxy prepreg is provided with through holes by lasermachining, the through holes are filled with a conductive paste, andthen a copper foil is laminated and patterning is carried out. Thissubstrate is used as a core, and is impregnated by prepregs with aconductive paste, to thus form a multi-layer structure.

As mentioned above, similar to the above-mentioned multi-layer ceramicwiring pattern, the connection method using IVHs for, for example, aresin based printing wiring substrate, allows an electrical connectiononly between the layers necessary to be connected. Furthermore, since nothrough holes are provided on the top layer of the substrate, themountability is also excellent.

However, in general, such a high-density mounted resin based printingwiring substrate including an IVH structure has a low thermalconductivity. As the mounting density of components becomes higher, itis getting more difficult to release heat that has been generated in thecomponents.

In addition, in the year 2000, a clock frequency of a CPU is about 1GHz. It is estimated that with the sophistication in the function of theCPU, its electric power consumption accordingly reaches 100 to 150 W perchip.

In general, a ceramic wiring substrate excellent in the thermalconductivity has an excellent heat releasing property, but there aresome disadvantages, for example, it is relatively expensive, it is poorin impact resistance property when it is applicable for a substrate or amodule used for portable terminals, and the like.

Therefore, in order to solve the problem of the thermal conductivity ofthe resin based printing wiring substrate, or in order to form acapacitor on the resin multi-layered substrate, a structure in which aresin based wiring substrate and a ceramic substrate are laminated isproposed in specification of Japanese Patent No. 3063427 or JP7(1995)-142867.

Furthermore, a multi-layered composite wiring substrate for enhancingthe thermal conductivity of a base material itself is disclosed in JP9(1997)-270584A, JP8 (1996)-125291A, JP8 (1996)-288596A, JP10(1998)-173097A, etc. This multi-layered composite substrate is formed bymixing a thermosetting resin such as an epoxy resin and an inorganicfiller having an excellent thermal conductivity (for example, a ceramicpowder, etc.) to make a composite. This substrate can contain aninorganic filler with high density, so that the thermal conductivity canbe enhanced. Furthermore, by selecting a suitable inorganic filler, forexample, the dielectric constant, the coefficient of thermal expansion,or the like, can be controlled suitably.

On the other hand, in developing the high density mounting of thesubstrate, the formation of a fine wiring pattern is important. Agenerally used method for forming the wiring pattern in themulti-layered ceramic wiring substrate includes, for example, a screenprinting of a thick film conductive paste onto the ceramic substratefollowed by firing for hardening. However, in this screen printingmethod, it is said that the mass production of wiring patterns having aline width of 100 μm or less is difficult.

Furthermore, in a usual printing wiring substrate, for example, a wiringpattern is formed by a subtractive method. In this subtractive method,the wiring pattern is formed by chemically etching a copper foil havinga thickness of about 18 to 35 μm. Also in this case, it is said that themass production of the wiring patterns having a line width of 75 μm orless is difficult. In order to make the wiring pattern finer, the copperfoil is required to be thin.

Furthermore, in the subtractive method, since the wiring pattern isprojected to the surface of the substrate, it is difficult to mount asolder or conductive adhesives, etc. for an electric connection on thebump formed on a semiconductor device. Furthermore, the bump moves to aplace between the wiring patterns, which may lead to a short circuit.Furthermore, the projected wiring patterns may damage the sealing with asealing resin in a later process.

In addition, in the printing wiring pattern by the build-up method,besides the subtractive method, an additive method tends to be employed.By the additive method, wiring patterns are plated selectively on thesurface of a substrate on which resist is formed. This allows theformation of wiring patterns having a line width of about 30 μm.However, the additive method has a problem in that the adhesive strengthof the wiring patterns to the substrate is lower as compared with thesubtractive method.

A method is proposed in which fine wiring patterns that have been formedbeforehand are subjected to a pattern test, and only excellent wiringpatterns are transferred to the desired substrate. For example, U.S.Pat. No. 5,407,511 discloses a method in which a fine wiring patternthat has been formed beforehand on the surface of a carbon plate isformed by printing or firing, and then transferred to a ceramicsubstrate. Furthermore, JP10(1998)-84186A, and JP10(1998)-41611 disclosea method of transferring a copper foil wiring pattern that has beenformed on a mold release support plate to a prepreg. Similarly,JP11(1999)-261219A discloses a method of transferring a copper foilwiring pattern to the mold release support plate formed of a copper foilvia a peel layer made of nickel-phosphorus alloy. Furthermore,JP8(1996)-330709A discloses a method of transferring a copper foilwiring pattern to a substrate by utilizing a difference in adhesivedegree between a roughened surface and a bright surface.

In the wiring patterns transferred by such transferring methods, awiring pattern is embedded in the surface of the substrate, so that thesubstrate surface becomes flat and can avoid the problem due to theprojection of the wiring pattern. Furthermore, JP10(1998)-190191Adiscloses an effect of compressing a conductive via paste to be filledin through holes by an amount of the thickness of the wiring patternwhen the wiring pattern is embedded in the surface of the substrate.

In recent years, a further fining of the wiring pattern is demanded.However, it is difficult to form a finer wiring pattern on the moldrelease support plate by conventional techniques for transferring thewiring pattern. Namely, for example, when a copper foil adhered to themold release support plate is formed into a pattern, if the adhesivestrength of the copper foil with respect to the mold release supportplate is weak, the fine wiring pattern is peeled off in a chemicaletching process. On the contrary, in a case where the adhesive strengthis strong, after the transfer of the wiring pattern to the substrate,when the mold release support plate is peeled off, the wiring pattern ispeeled off together. Furthermore, there is also a method in which thesurface of the copper foil is roughened so as to make the adhesivestrength between the copper foil and the substrate stronger than theadhesive strength between the copper foil and the release moldingsupport plate, thereby transferring the copper foil onto the substrate.However, with this method, it is difficult to form a fine wiringpattern.

Furthermore, in sintering the conductive paste containing a conductivepowder, unlike a metal layer such as a copper foil, the electricconductivity is poor, which may lead to a problem about a trend toward ahigh frequency in the future.

On the contrary, conventionally, it was difficult to form a ceramicmulti-layered substrate in which a wiring pattern is formed of a metalfoil such as a copper foil, etc. because the formation of a wiringpattern by the use of a metal foil on a green sheet without damaging theproperty of the green sheet is difficult.

Furthermore, in a production method of the resin based printing wiringpattern, conventionally, a general method is to laminate layerssequentially. A plurality of press processes are needed. Therefore, inorder to realize an accurate interlayer connection, complicated stepsfor correcting hardening and shrinkage occurring in each press processcannot be avoided.

Furthermore, for the purpose of solving the problem of the thermalconductivity of the resin printing wiring substrate, or for forming acapacitor with a capacitance on the resin multi-layered substrate, alaminated structure itself of a resin printing wiring substrate and aceramic substrate has been proposed. However, in fact, since damagessuch as cracks are generated mainly in the ceramic layer through thelaminating process etc., it was difficult to realize this structure.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a wiring patternformation and transfer material, which transfers a fine wiring patternto a substrate, more particularly, to a wiring pattern formation andtransfer material capable of transferring a fine wiring pattern to asubstrate easily and reliably and at a low cost.

In addition, in order to advance the high density mounting, it isimportant not only to make a wiring pattern to be fine but also to formand mount circuit components connecting to a wiring pattern.Conventionally, a passive component such as an inductor, a capacitor, aresistor, or the like, is mounted generally on the surface of thesubstrate. And it was difficult to incorporate such passive componentsinto the substrate. Therefore, there was a limitation to high densitymounting.

For example, in the conventional method disclosed in the above-mentionedofficial gazettes, etc., the pattern formed on the transfer material isonly a wiring portion such as a copper foil. In order to enhance themounting density, a method of mounting the passive components in a formof a chip can be proposed. However, in embedding the passive components,etc. into the substrate, there arise some problems of breakage of linebetween the wiring pattern and the connection portion, the dislocationof chip, and the like.

It is another object of the present invention to provide a wiringpattern formation and transfer material for incorporating a fine wiringpattern or circuit components into a circuit substrate, morespecifically, a wiring pattern formation and transfer material capableof mounting a circuit component etc. on the circuit substrate accuratelyand at a low cost.

It is a further object of the present invention to provide a wiringpattern on which a wiring pattern and circuit components are formed bythe use of a wiring pattern formation and transfer material or a wiringpattern and circuit component formation and transfer material.

In order to achieve the above-mentioned object, a transfer materialaccording to the first configuration of the present invention includesat least three layers of a first metal layer as a carrier, a secondmetal layer as a wiring pattern, and a peel layer that is sandwichedbetween the first metal layer and the second metal layer and allows thefirst metal layer and the second metal layer to be adhered releasably,wherein a convex portion corresponding to the wiring pattern is formedon the surface portion of the first metal layer, and the peel layer andthe second metal layer are formed on a region of the convex portions.

A transfer material according to the second configuration of the presentinvention includes a transfer material including at least two layers, afirst metal layer as a carrier, and a second metal layer as a wiringpattern, wherein a circuit component is formed on the first metal layerby a printing method for electrically connecting to the second metallayer.

Furthermore, in order to achieve the object, a first method forproducing a transfer material of the present invention includes forminga peel layer on a first metal layer, forming a second metal layer on thepeel layer, and etching the second metal layer, the peel layer and thesurface portion of the first metal layer by a chemical etching process,thereby forming the second metal layer and the peel layer into thewiring pattern, and at the same time, forming a convex and concaveportion having a convex portion corresponding to the wiring pattern onthe surface portion of the first metal layer.

With the transfer material of the second configuration, it is possibleto form circuit components such as an inductor, a capacitor, and aresistor, etc. by printing in one process. In particular, the formationof the resistor becomes easy. Moreover, the circuit components are notnecessarily limited to these passive materials, and an active componentsuch as a semiconductor chip, etc. can be formed.

Furthermore, mounting of the circuit components by using a solder etc.becomes unnecessary, thus simplifying a mounting process. Furthermore,since the soldering connection is reduced, the reliability of the wiringsubstrate can be improved. Furthermore, since the circuit components areformed on the transfer material by printing, as compared with the casewhere component chips are mounted by soldering, the height of thecircuit components can be reduced, thus facilitating the transfer whileembedding the components into the substrate and the integration of thecomponents into the substrate. Furthermore, the circuit components canbe placed freely, for example, it is possible to make the wiringdistance from the circuit components to the integrating capacitor, etc.the shortest, thereby improving the high frequency property.

Furthermore, in the transfer material of the second configuration, aftertransfer, by forming new second metal layer or wiring pattern orcomponent pattern on the first metal layer that is a peeled carrier, itis possible to reuse the first metal layer. And the configuration of thewiring pattern is not particularly limited. Therefore, low cost can berealized, and furthermore, it is useful from the viewpoint of industrialapplicability.

Furthermore, a first method for producing a transfer material of thepresent invention includes forming a second metal layer into a wiringpattern on the first metal layer, and forming a circuit component by aprinting method for electrically connecting to the second metal layer.

Furthermore, a second method for producing a transfer material of thepresent invention includes forming a peel layer and a second metal layeron a first metal layer, processing the second metal layer and the peellayer into a wiring pattern, and forming a circuit component by aprinting method on the second metal layer for electrically connectingthe second metal layer.

The second metal layer that is a wiring pattern can be formed directlyon the first metal layer that is a carrier by a plating method, anevaporation method, a sputtering method, or the like. At the formationof the second meat layer, similarly, a thin resistor film can be formedby a sputtering method, and the like.

Furthermore, a third method for producing a transfer material of thepresent invention includes an electrically insulating substrate, and awiring pattern formed on at least one principal plane of theelectrically insulating substrate by a transfer method by the use of thetransfer material according to the first configuration, wherein thewiring pattern is formed in the concave portion formed on the principalplane.

Furthermore, a wiring substrate according to the second configuration ofthe present invention has an inner via hole structure in which aplurality of wiring substrates are laminated, wherein at least one layerhas a wiring substrate according to the first configuration.

Furthermore, a wiring substrate according to the third configuration ofthe present invention includes an electrically insulating substrate, anda wiring pattern and a circuit component that are formed on at least oneprincipal plane of the electrically insulating substrate by a transfermethod by the use of the transfer material according to the secondconfiguration, wherein the circuit component is electrically connectedto the wiring pattern, and the circuit component and the wiring patternare embedded in the principal plane.

Furthermore, a wiring substrate according to the fourth configuration ofthe present invention has an inner via hole structure in which aplurality of wiring substrates are laminated, wherein at least one layerhas a wiring substrate according to the third configuration.

Furthermore, a first method for producing a wiring substrate of thepresent invention using the transfer material according to the firstconfiguration includes pressing the side of the transfer material wherethe wiring pattern metal layer including at least a second metal layeris formed onto at least one principal plane of an uncured base materialsheet, and peeling off a first metal layer adhered to the second metallayer from the second metal layer, thereby transferring the wiringpattern metal layer to the base material sheet.

Furthermore, a second method for producing a wiring substrate of thepresent invention includes providing a ceramic sheet with a throughhole, placing a constrained sheet, having an inorganic composition thatsubstantially is not sintered nor shrunk at the firing temperature ofthe ceramic sheet as a main component, on both surfaces of the ceramicsheet provided with a through hole, firing the ceramic sheet togetherwith the constrained sheet, after firing, removing the constrainedsheet, filling the through hole with a thermosetting conductivecomposition so as to form a ceramic substrate having a via conductor,pressing the side where the wiring pattern metal layer including atleast a second metal layer is formed of the transfer material accordingto the first configuration onto at least one principal plane of anuncured base material sheet including a thermosetting resin composition,peeling off the first metal layer adhered to the second metal layer viathe peel layer from the second metal layer, thereby transferring thewiring pattern metal layer to the base material sheet, providing a basematerial sheet including the thermosetting resin composition with athrough hole before or after the transfer, filling the through hole witha conductive composition so as to form a composite wiring substratehaving a via conductor, laminating the ceramic substrate and thecomposite wiring substrate, and heating and pressing the laminate so asto form a multi-layered wiring substrate.

Furthermore, a third method for producing a wiring substrate of thepresent invention using the transfer material according to the secondconfiguration includes: pressing the side of the transfer material wherethe wiring pattern metal layer including at least a second metal layeris formed onto at least one principal plane of an uncured base materialsheet, and peeling off the first metal layer, thereby transferring atleast the second metal layer and the circuit component to the basematerial sheet.

Furthermore, a fourth method for producing a wiring substrate of thepresent invention includes providing a ceramic sheet with a throughhole, placing a constrained sheet, having an inorganic composition thatsubstantially is not sintered nor shrunk at the firing temperature ofthe ceramic sheet as a main component, on both surfaces of the ceramicsheet provided with a through hole, firing the ceramic sheet togetherwith the constrained sheet, after firing, removing the constrainedsheet, filling the through hole with a thermosetting conductivecomposition so as to form a ceramic substrate having a via conductor,pressing the side where the wiring pattern metal layer including atleast a second metal layer is formed of the transfer material accordingto the second configuration onto at least one principal plane of anuncured base material sheet including a thermosetting resin composition,peeling off the first metal layer adhered to the second metal layer viathe peel layer from the second metal layer, thereby transferring thewiring pattern metal layer to the base material sheet, providing a basematerial sheet including the thermosetting resin composition with athrough holes before or after the transfer, filling the through holewith a conductive composition so as to form a composite wiring substratehaving a via conductor, laminating the ceramic substrate and thecomposite wiring substrate, and heating and pressing the laminate so asto form a multi-layered wiring substrate.

With the transfer material of the second configuration, it is possibleto transfer the circuit components onto any of the layers of themulti-layered substrate, and further the components can be placedfreely. Therefore, the degree of freedom in designing the electriccircuit is radically improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a schematic configuration of awiring pattern formation and transfer material (hereinafter, a transfermaterial will be referred to) (a first transfer material) according to afirst embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a schematic configuration of atransfer material (a second transfer material) according to a secondembodiment of the present invention.

FIG. 3 is a cross-sectional view showing a schematic configuration of atransfer material (a third transfer material) according to a thirdembodiment of the present invention.

FIGS. 4A to 4F are cross-sectional views schematically showing a processfor producing the first transfer material.

FIGS. 5A to 5E are cross-sectional views schematically showing a processfor producing the second transfer material.

FIGS. 6A to 6E are cross-sectional views schematically showing a processfor producing the third transfer material.

FIGS. 7A to 7C are cross-sectional views schematically showing a processfor producing a composite wiring substrate using the transfer materialof the present invention.

FIG. 8 is a cross-sectional view showing a schematic configuration of aceramic wiring substrate produced by using the transfer material of thepresent invention.

FIG. 9 is a cross-sectional view showing a schematic configuration ofthe ceramic wiring substrate shown in FIG. 8 on which a semiconductorchip is flip-chip mounted.

FIGS. 10A to 10J are cross-sectional views schematically showing oneexample of a process for producing a multi-layered wiring substrateusing the transfer material of the present invention.

FIG. 11 is a cross-sectional view showing one example of a schematicconfiguration of the multi-layered wiring substrate produced by usingthe transfer material of the present invention.

FIG. 12 is a cross-sectional view showing another example of a schematicconfiguration of the multi-layered wiring substrate produced by usingthe transfer material of the present invention.

FIG. 13 is a cross-sectional view showing a further example of aschematic configuration of the multi-layered wiring substrate producedby using the transfer material of the present invention.

FIG. 14 is a cross-sectional view showing a still further example of aschematic configuration of the multi-layered wiring substrate producedby using the transfer material of the present invention.

FIG. 15 is a cross-sectional view showing a further example of aschematic configuration of the multi-layered wiring substrate producedby using the transfer material of the present invention.

FIGS. 16A to 16C are cross-sectional views schematically showing oneexample of a process for producing a multi-layered wiring substrateusing the transfer material of the present invention.

FIGS. 17A to 17C are cross-sectional views schematically showing anotherexample of a process for producing a multi-layered wiring substrateusing the transfer material of the present invention.

FIGS. 18A to 18E are cross-sectional views schematically showing afurther example of a process for producing a multi-layered wiringsubstrate using the transfer material of the present invention.

FIGS. 19A and 19B are cross-sectional views showing a schematicconfiguration of a circuit component and wiring pattern formation andtransfer material (a fourth transfer material) according to a fifthembodiment of the present invention.

FIG. 20 is a cross-sectional view showing a schematic configuration of acircuit component and wiring pattern formation and transfer material (afifth transfer material) according to a sixth embodiment of the presentinvention.

FIG. 21 is a cross-sectional view showing a schematic configuration of acircuit component and wiring pattern formation and transfer material (asixth transfer material) according to a seventh embodiment of thepresent invention.

FIGS. 22A to 22G′ are cross-sectional views schematically showing aprocess for producing a multi-layered circuit component using the fourthtransfer material of the present invention.

FIGS. 23A to 23H are cross-sectional views schematically showing aprocess for producing a multi-layered circuit component using the fifthtransfer material of the present invention.

FIGS. 24A to 24H are cross-sectional views schematically showing anoutline process for producing a multi-layered circuit component usingthe sixth transfer material of the present invention.

FIG. 25 is a cross-sectional view showing a multi-layered circuitsubstrate produced by using the fourth to sixth transfer materials.

FIGS. 26A to 26C are cross-sectional views schematically showing aprocess for producing a single layered wiring substrate that forms eachlayer of the multi-layered circuit substrate shown in FIG. 25 by usingthe sixth transfer material of the present invention; FIGS. 26A′ to 26C′are cross-sectional views showing each layer of the multi-layeredcircuit substrate produced by the process shown in FIG. 26A to 26C; andFIG. 26D′ is a cross-sectional view showing a bottom layer wiringsubstrate of the multi-layered circuit substrate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described more specificallywith reference to embodiments.

First Embodiment

One example of a wiring pattern formation and transfer materialaccording to a first embodiment of the present invention (hereinafter, afirst transfer material will be referred to) is described. FIG. 1 is across-sectional view showing a schematic configuration of the firsttransfer material.

As shown in FIG. 1, the first transfer material includes a first metallayer 101 having a concave and convex portion (for example, the heightof the convex portion is about 1 to 12 μm) on a surface portion thereof.The convex portion of the first metal layer 101 corresponds to a wiringpattern. A peel layer 102 made of an organic layer or a metal platinglayer and a second metal layer 103 are formed on the convex portions.Namely, the first transfer material has a three-layered structure inwhich the first metal layer 101 is adhered to the second metal layer 103with the peel layer 102 sandwiched therebetween.

In the first transfer material, the second metal layer 103 is awiring-pattern and the first metal layer 101 serves as a carrier fortransferring the wiring pattern to a substrate. The first metal layer101 transfers the second metal layer 103 that is a wiring pattern to thesubstrate, and then the first metal layer 101 is peeled off from thesubstrate together with the peel layer 102.

For example, a method for producing the first transfer material includesthe steps of:

-   -   (a) forming a three-layered structure by forming the second        metal layer containing the same metal component as that        contained in the first metal layer on the first metal layer with        the peel layer made of an organic layer or a metal plating layer        sandwiched between the first and second metal layers; and    -   (b) processing not only the second metal layer and the peel        layer but also the surface portion of the first metal layer into        the wiring pattern by a chemical etching process, thus to form a        concave and convex portion on the surface portion of the first        metal layer.

With this production method, it is possible to form the second metallayer into a fine wiring pattern by a chemical etching process such asphotolithography, etc. Furthermore, since a metal foil forming thewiring pattern (second metal layer) contains the same material as thatcontained in the metal foil forming a carrier (first metal layer), it ispossible to form the convex and concave portion having the same patternas the wiring pattern of the second metal layer on the first metal layerthat forms the carrier in one etching process.

Furthermore, in the first transfer material of this embodiment, the sametransfer material can be reproduced by reusing the first metal layerpeeled off after use, and by forming the second metal layer having thesame shape as the convex portion of the first metal layer on the firstmetal layer with the peel layer such as a plating layer etc. sandwichedbetween the first and second metal layers. The first metal layer alsocan be reused for the other applications of use, for example, for apattern formation material for a letterpress printing method. Therefore,since the first transfer material of this embodiment can make effectiveuse of resources, it is advantageous from the viewpoint of savingresources and reducing waste. The same is true in the second and thirdtransfer materials described in the other embodiments.

Moreover, it is also possible to form circuit components such as aninductor, a capacitor, a resistor, a semiconductor device, or the like,for electrically connecting to the wiring pattern of the transfermaterial of this embodiment, and to transfer them to the substratetogether with the wiring pattern. It is preferable that the passivecomponents such as inductor, capacitor, and resistor, etc. are formed onthe substrate by a printing method, for example a screen printingmethod.

Second Embodiment

One example of a transfer material according to a second embodiment ofthe present invention (hereinafter, a second transfer material will bereferred to) is described. FIG. 2 is a cross-sectional view showing aschematic configuration of the second transfer material.

As shown in FIG. 2, the second transfer material includes a first metallayer 101 having a concave and convex portion on a surface portionthereof. The convex portion corresponds to a wiring pattern. The secondtransfer material has a four-layered structure in which a peel layer 102made of an organic layer or a metal plating layer and a second metallayer 103 are formed on the convex portion, and further a third metallayer 104 is formed on the second metal layer 103. The first metal layer101 is adhered to the second metal layer 103 with the peel layer 102sandwiched therebetween.

In the second transfer material, the second metal layer 103 and thethird metal layer 104 make a two-layered wiring pattern and the firstmetal layer 101 serves as a carrier for transferring the wiring patternto the substrate. Therefore, the first metal layer 101 transfers thesecond metal layer 103 and the third metal layer 104, which are thewiring patterns, to the substrate, and then is peeled off from thesubstrate together with the peel layer 102.

For example, a method for producing the second transfer materialincludes steps of:

-   -   (a) forming a three-layered structure by forming the second        metal layer containing the same metal component as that        contained in the first metal layer on the first metal layer with        the peel layer made of an organic layer or a metal plating layer        sandwiched between the first and second metal layers;    -   (b) forming a plating resist on an arbitrary region on the        second metal layer so as to make an exposed region that is not        covered with the plating resist into a wiring pattern;    -   (c) forming the third metal layer made of a plating layer on the        exposed region of the wiring pattern on the surface of the        second metal layer by pattern plating;    -   (d) forming the third metal layer into the convex portion of the        wiring pattern on the second metal layer by peeling off the        plating resist; and    -   (e) selectively removing, by a chemical etching process, the        second metal layer, the peel layer, and the upper part of the        first metal layer of the region in which the third metal layer        is not formed.

In this producing method, when the same metal component as the secondmetal layer is used for the third metal layer, for example, when acopper plating layer (third metal layer) is formed on the copper foil(second metal layer), it is possible to form the second and third metallayers into a fine wiring pattern for the reason as mentioned in thefirst embodiment and further because an additive method is employed.

Furthermore, since the second metal layer and the peel layer are thinnerthan the third metal layer, they can be removed in a short-time etching.Basically, the third metal layer can be maintained with the thickness ofthe third metal layer hardly reduced. Therefore, the thickness of thewiring pattern can be controlled freely.

On the other hand, when a metal different from that of the second metallayer is used for the third metal layer, for example, when a gold (thirdmetal layer) is formed on the copper foil (second metal layer) bypattern plating, the third metal layer serves as an etching resist.Therefore, it is possible to remove selectively the second metal layer,the peel layer, and the upper surface of the first metal layer on theregion in which the third metal layer having the wiring pattern is notformed. Furthermore, when gold is used for the third metal layer, thetop layer of the wiring pattern of the transfer material is gold.Therefore, when for example, a bare chip, a bare SAW (Surface AcousticWave) filter, or the like is flip-chip mounted on the wiring pattern, alow resistance and stable connection can be realized. Moreover, the sameeffect can be obtained when silver is used for the third metal layer.

Moreover, it is preferable in the production method that before thethird metal layer is formed on the second metal layer, the surface ofthe second metal layer is roughened. The term “before the third metallayer is formed” means that before the plating resist as a mask forforming the wiring pattern is formed on the second metal layer, orbefore the third metal layer is formed along the wiring pattern on thesecond metal layer on which masking is performed in the wiring pattern.In this way, when the surface of the second metal layer is roughened,the adhesion between the second metal layer and the third metal layer isimproved.

It is preferable in the production method that the third metal layer isformed on the second metal layer by electrolytic plating. When the thirdmetal layer or the metal layer for forming a wiring pattern is formed byelectrolytic plating, appropriate adhesion can be obtained on theadhering surface between the second metal layer and the third metallayer. Furthermore, even if, for example, the etching process, etc. iscarried out, no gap occurs between the metal layers, so that anexcellent wiring pattern can be formed. On the other hand, the patternmay be formed by masking the wiring pattern after the third metal layeris formed on the second metal layer by panel plating. This case providesan effect of preventing the surface oxidization of the second metallayer after transfer and improving the soldering wettability.

It is preferable in the production method that the second and thirdmetal layers as well as the surface of the first metal layer areprocessed into the wiring pattern by a chemical etching process.

For the same reason as mentioned above, it is preferable in theproduction method that the second metal layer includes at least onemetal selected from the group consisting of copper, aluminum, silver andnickel, particularly, copper. It is desirable that the first metal layerincludes the same metal component as the second metal component becausethe convex portion having the same shape as that of the wiring pattern(second metal layer) is formed on the surface of the first metal layer,because a convex portion having the same shape as the wiring pattern(second metal layer) is formed on the surface of the first metal layerwhen the second metal layer is etched by a chemical etching process. Inparticular, the first and second metal layers are formed of a copperfoil, and more preferably, an electrolytic copper foil.

The method for producing the first and second metal layers is notparticularly limited. For example, the well-known method for producingmetal foil can be employed.

For a treatment for roughening the surface, for example, a blackeningtreatment, a soft etching treatment, a sandblast treatment, and thelike, can be employed.

Moreover, it is also possible to form circuit components such as aninductor, a capacitor, a resistor, a semiconductor device, or the like,for electrically connecting to the wiring pattern of the transfermaterial of this embodiment, and to transfer them to the substratetogether with the wiring pattern. It is preferable that the passivecomponents such as inductor, capacitor, and resistor, etc. are formed onthe substrate by a printing method, for example a screen printingmethod.

Third Embodiment

One example of a transfer material according to a third embodiment ofthe present invention (hereinafter, a third transfer material will bereferred to) is described. FIG. 3 is a cross-sectional view showing aschematic configuration of the third transfer material.

As shown in FIG. 3, the third transfer material includes a first metallayer 101 having a concave and convex portion on a surface portionthereof. The convex portion corresponds to a wiring pattern. The thirdtransfer material has a five-layered structure in which a peel layer 102made of an organic layer or a metal plating layer and a second metallayer 103 are formed on the convex portion, further a third metal layer104 is formed thereon, and further a fourth metal layer 105 is formedthereon. The first metal layer 101 is adhered to the second metal layer103 via the peel layer 102.

In the third transfer material, the second metal layer 103, the thirdmetal layer 104 and the fourth metal layer 105 make a three-layeredwiring pattern. The first metal layer 101 serves as a carrier fortransferring the wiring pattern to the substrate. The first metal layer101 transfers the second metal layer 103, the third metal layer 104 andthe fourth metal layer 105, which serve as the wiring pattern, to thesubstrate, and then is peeled off from the substrate together with thepeel layer 102.

For example, a method for producing the third transfer material includesthe steps of:

-   -   (a) forming a three-layered structure by forming the second        metal layer containing the same metal component as the first        metal layer on the first metal layer with a peel layer        sandwiched between the first and second metal layers;    -   (b) forming a plating resist on an arbitrary region on the        second metal layer so as to make an exposed region that is not        covered with the plating resist into a wiring pattern;    -   (c) forming the third metal layer made of a plating layer on the        exposed region of the wiring pattern on the surface of the        second metal layer;    -   (d) on the third metal layer, forming a fourth metal layer of a        metal component that is different from the components of the        first to third metal layers and that is chemically stable with        respect to an etching liquid corroding the first to third metal        layers;    -   (e) forming the third and fourth metal layers into a convex        portion of the wiring pattern by peeling off the plating resist;        and

(f) selectively removing the second metal layer, the peel layer, and theupper part of the first metal layer of the region in which the third andfourth metal layers are not formed by a chemical etching process.

With this production method, it is possible to form a fine wiringpattern for the reason as mentioned in the first embodiment and furtherbecause an additive method is employed. Furthermore, the thickness ofthe wiring pattern can be controlled freely.

It is preferable in the production method that before the third metallayer is formed on the second metal layer, the surface of the secondmetal layer is roughened. The term “before the third metal layer isformed” means that before the plating resist for forming the wiringpattern is formed on the second metal layer, or before the third metallayer is formed along the wiring pattern on the second metal layer onwhich masking is performed in the wiring pattern. In this way, when thesurface of the second metal layer is roughened, the adhesion between thesecond metal layer and the third metal layer is improved.

It is preferable in the production method that the third metal layer isformed on the second metal layer by electrolytic plating. When the thirdmetal layer or the metal layer for forming the wiring pattern is formedby electrolytic plating, appropriate adhesion can be obtained on theadhering surface between the second metal layer and the third metallayer. Furthermore, even if, for example, the etching process etc. iscarried out, no gap occurs between the metal layers, so that anexcellent wiring pattern can be formed.

On the other hand, the pattern may be formed by masking on the wiringpattern after the third metal layer is formed on the second metal layerby panel plating. This case provides an effect of preventing the surfaceoxidation of the second metal layer after transfer and improving thesoldering wettability.

Furthermore, it is preferable in the production method that the fourthmetal layer is formed on the third metal layer by electrolytic plating.It is preferable that as a material for the fourth metal layer, byselecting a component that is different from the components of the firstto third metal layers, that is, a metal component chemically stable withrespect to an etching liquid corroding the first to third metal layers,the second, third, and fourth metal layers can be processed into thewiring pattern together with the surface portion of the first metallayer without reducing the thickness even in the chemical etchingprocess of the step (f).

For the same reason mentioned above, it is preferable in the productionmethod that the second and third metal layers include at least one metalselected from the group consisting of copper, aluminum, silver andnickel, particularly, copper. It is desirable that the first metal layercontains the same metal component as the component contained in thesecond metal component because a convex portion having the same shape asthe wiring pattern (second metal layer) is formed on the surface of thefirst metal layer when the second metal layer is etched by a chemicaletching process. In particular, these metal layers are formed of acopper foil, more preferably, an electrolytic copper foil. On the otherhand, a preferable example of the fourth metal layer includes, forexample, a plating layer of Ag, Au, or the like, having chemicalstability and the low resistance property.

The method for producing the first and second metal layers is notparticularly limited. For example, the well-known method for producing ametal foil can be employed.

For a treatment for roughening the surface, for example, a blackeningtreatment, a soft etching treatment, a sandblast treatment, and the likecan be employed.

Moreover, it is preferable in the above-mentioned first, second, andthird transfer materials of the first to third embodiments that theadhesive strength between the first metal layer and the second metallayer via the peel layer is weak, for example, 50 N/m (gf/cm) or less.As the peel layer, an organic layer having adhesive strength and athickness of much thinner than 1 μm can be used. An example of the peellayer includes an urethane resin, an epoxy resin, a phenol resin, andthe like. However, the peel layer is not necessarily limited thereto,and other resin such as a thermoplastic resin can be used. However, thepeel layer having a thickness of 1 μm or more deteriorates the peelingproperty, which may make the transfer difficult.

Furthermore, in order to lower the adhesiveness in the first to thirdtransfer materials intentionally, a plating layer may be interposed asthe peel layer. A metal plating layer having a thickness of much thinnerthan 1 m, for example, a nickel plating layer, a nickel-phosphorousalloy layer, an aluminum plating layer, a chrome plating layer, or thelike, can be interposed between the copper foils (first and second metallayers) so as to provide a peeling property. This facilitates peelingoff the second metal layer from the first metal layer after the secondmetal layer is transferred to the substrate, thus transferring only thesecond metal layer to the substrate. A suitable thickness of the peellayer formed of the metal layer is about 100 nm to 1 μm. Since the costof the process is increased with the increase in thickness, thethickness is desirably less than 1 μm.

Furthermore, in the first to third transfer materials, if the peel layerintentionally is formed by Au plating so that it can be peeled off fromthe first metal layer easily, when the first metal layer is peeled offfrom the substrate after transfer the peel layer remains on the surfaceof the second metal layer of the wiring pattern. Thus, a wiring patternwhose surface is Au plating treated can be obtained. The wiring patternexhibits an excellent FC mounting (flip-chip mounting) property,components mounting property, and the like.

Furthermore, it is preferable in the first to third transfer materialsthat the first metal layer includes at least one metal selected from thegroup consisting of copper, aluminum, silver and nickel, andparticularly preferably copper. It is preferable that the second metallayer, as in the first metal layer, includes at least one metal selectedfrom the group consisting of copper, aluminum, silver and nickel, andparticularly preferably, copper. Moreover, the metals may be one kind,or may be two kinds or more.

Furthermore, it is preferable in the first to third transfer materialsthat the first metal layer includes the same metal component as thesecond metal because two-layered structure of metal layers are processedat the same time when, for example, an etching process is carried out.In this case, since there is no difference in the coefficient of thermalexpansion between the first metal layer and the second metal layer, thepattern distortion is not likely to occur when heating. Therefore, it issuitable for the transfer of the fine wiring pattern. When the platinglayer is used for the peel layer, desirably, a copper etching liquid canbe used for processing. However, the kinds of metal are not particularlylimited as long as the first and the second meals include the samematerials. However, preferably they are formed of a copper foil, andmore preferably an electrolytic copper foil because of its excellentconductivity. Moreover, the metals may be one kind, or may be two kindsor more.

Furthermore, in the first to third transfer materials, the averageroughness (Ra) of the center line of the surface of the second metallayer is 2 μm or more, and more preferably 3 μm or more. In the firsttransfer material, when the average roughness (Ra) of the center line ofthe surface is less than 2 μm, the adhesion with respect to thesubstrate to be transferred may be insufficient. On the other hand, inthe second and third transfer materials, when the average roughness (Ra)of the center line of the surface is less than 2 μm, the adhesionbetween the metal layers forming the multi-layered wiring pattern maybecome insufficient, and the etching liquid may enter the gap betweenthe metal layers so as to make the wiring pattern deficient.

Furthermore, in the first to third transfer materials, the thickness ofthe second metal layer is preferably 1 to 18 μm, and more preferably 3to 12 μm. When the thickness is less than 3 μm, when the second metallayer is transferred to the substrate, an excellent electricconductivity may not be exhibited. On the contrary, when the thicknessis 18 μm or more, it may be difficult to form a fine wiring pattern.

Furthermore, in the first to third transfer materials, the thickness ofthe first metal layer is preferably 4 to 40 μm, and more preferably 20to 40 μm. The first metal layer serves as a carrier, and at the sametime has a structure in which the surface layer portion is etched likethe wiring layer so as to have a convex and concave portion. Therefore,the first metal layer is desired to have a sufficient thickness.Furthermore, since the first to third transfer materials have a carriermade of a metal layer (first metal layer), they exhibit the sufficientmechanical strength or thermal resistance with respect to the thermaldistortion or stress distortion in the direction of the plane, which aregenerated at the time of transfer.

The total thickness of the first to third transfer materials ispreferably 40 to 150 μm, and more preferably 40 to 80 μm. Furthermore,the line width of the wiring pattern generally is required to be aboutup to 25 μm, as a fine line width. Also in the present invention, such aline width is preferable.

Moreover, it is also possible to form circuit components such as aninductor, a capacitor, a resistor, a semiconductor device, or the like,for electrically connecting to the wiring pattern of the transfermaterial of this embodiment and to transfer them to the substratetogether with the wiring pattern. It is preferable that the passivecomponents such as inductor, capacitor, and resistor, etc. are formed onthe substrate by a printing method, for example a screen printingmethod.

Fourth Embodiment

In this embodiment, a method for producing the wiring substrate usingthe various kinds of wiring pattern formation and transfer materials ofthe present invention (first to third transfer materials), and a wiringsubstrate produced by the production method will be described.

The following are two methods for producing the wiring substrate usingthe transfer materials according to the present invention.

A first method includes the following steps:

-   -   (h) preparing at least one of the first to third transfer        materials described in the first to third embodiments and        placing the material(s) so that the wiring layer side (side on        which the second metal layer etc. is formed) of the material is        in contact with at least one surface of a base material sheet (a        material for the substrate) so as to adhere thereto, and    -   (i) transferring only the wiring layer to the base material        sheet by peeling off the first metal layer from the transfer        material.

Thus, it is possible to produce a wiring substrate on which fine wiringpatterns are formed in the concave portion on the base material sheet.Furthermore, since the wiring portion of this wiring substrate has aconcave shape, this concave portion can be used for positioning. Thisconfiguration is excellent in, for example, the flip chip mounting etc.of a semiconductor.

Furthermore, the second production method is a method for producing amulti-layered substrate and includes a step for laminating two or moreof the wiring substrates produced by the first production method. Thefirst production method enables the transfer formation of the wiringpattern at a low temperature of 100° C. or less. Therefore, in any caseswhere a ceramic green sheet is used or where a thermosetting resin sheetis used for the base material sheet, it is possible to keep the sheetuncured even after the wiring pattern is transferred. This allows athermal curing and shrinking of the uncured wiring substrates togetherat a time after the uncured wiring substrates are laminated. Therefore,unlike a conventional method for producing a multi-layered substraterepeating the process in which the wiring substrate is laminated andsubjected to a curing and shrinking treatment one by one, the method forproducing this embodiment has an advantage in that it is not necessaryto correct the curing and shrinking with each layer. Therefore, thesteps can be simplified.

This method allows the formation of a multi-layered wiring substratehaving fine wiring patterns. However, in the multi-layered wiringsubstrate, the wiring patterns formed on the wiring substrate of theinside layer are not required to have a concave shape. Therefore, with atransfer material for forming this wiring pattern, the surface portionof the first metal layer is not necessarily formed in a concave andconvex shape and may be flat. In this case, for example, by controllingthe time of the chemical etching process in the formation of the wiringpattern, it is possible to stop the process at the stage in which thepeel layer is etched so as not to etch the first metal layer.Furthermore, when the peel layer is made of a plating layer containingNi, by using a base solution obtained by adding ammonium into copperchloride as an etching liquid, it is possible to remove only the copperfoil (wiring pattern) by an etching process and to remain the peellayer. This transfer material does not have a problem in the transferbecause a carrier copper foil (first metal layer) is peeled off afterbeing pressed onto the substrate, and the plating layer that is a peellayer also is peeled off together.

Furthermore, when the first transfer material is used, by pressing thefirst transfer material onto the base material sheet (a material for thesubstrate), the convex portions of the second metal layer and the firstmetal layer are embedded in the base material sheet. Thereafter, thefirst metal layer is peeled off, and then the wiring substrate has aconcave portion on the surface and the wiring layer made of the secondmetal layer at the bottom of the concave portion.

Furthermore, when the second transfer material is used by pressing thesecond transfer material onto the base material sheet, for example,after the entire part of the second and third metal layers and theconvex portion of the first metal layer are embedded in the basematerial sheet, the first metal layer is removed. This allows theproduction of the two-layered wiring substrate having a concave portionof a depth that is substantially the same as a thickness of the convexportion of the first metal layer, and the second and third metal layersformed on the bottom of the concave portion.

Similarly, when the third transfer material is used, for example, afterthe entire part of the second, third and fourth metal layers and theconvex portion of the first metal layer are embedded in the basematerial sheet, the first metal layer is removed. This allows theproduction of the three-layered wiring substrate having a concaveportion of the depth that is substantially the same as the thickness ofthe convex portion of the first metal layer, and the second, third andfourth metal layers formed on the bottom of the concave portion.

It is preferable in the method for producing the first and the secondwiring substrates that the base material sheet includes an inorganicfiller and the thermosetting resin composition and has at least onethrough hole which is filled with a conductive paste. This makes it easyto produce a composite wiring substrate for high-density mounting havingan excellent thermal conductivity and having an IVH structure in which,for example, wiring patterns of the both sides of the substrate areelectrically connected via the conductive paste. Furthermore, with theuse of this base material sheet, in the formation of the wiringsubstrate, high temperature is not required, but treating may be carriedout at a low temperature of, for example, about 200° C., i.e. the curingtemperature of the thermosetting resin.

The base material sheet preferably contains 70 to 95 weight % of aninorganic filler and 5 to 30 weight % of a thermosetting resin, and morepreferably contains 85 to 90 weight % of an inorganic filler and 10 to15 weight % of a thermosetting resin. Since the base material sheetcontains inorganic fillers with a high concentration, by changing thecontent of inorganic fillers, the coefficient of thermal expansion,thermal conductivity, dielectric constant, and the like, can be setarbitrarily.

It is preferable that the inorganic filler includes at least oneinorganic filler selected from the group consisting of Al₂O₃, MgO, BN,AlN and SiO₂. By determining the kinds of inorganic fillerappropriately, it is possible to set, for example, the coefficient ofthermal expansion, thermal conductivity, and dielectric constant to thedesirable conditions. For example, it is possible to set the coefficientof thermal expansion of the base material sheet in the plane directionto the same level of the coefficient of thermal expansion of asemiconductor to be mounted, and to provide a high thermal conductivity.

The base material sheet using, for example, Al₂O₃, BN, AlN and the like,among the inorganic fillers, is excellent in thermal conductivity. Thebase material sheet using MgO is excellent in thermal conductivity andcapable of raising the coefficient of thermal expansion. Furthermore,when SiO₂, particularly amorphous SiO₂, is used, a base material sheethaving a small constant thermal expansion, a light weight and lowdielectric constant can be obtained. Moreover, the inorganic filler canbe used singly or by combination of two kinds or more of the inorganicfillers.

The base material sheet including the inorganic filler and thethermosetting resin composition can be produced by, for example, thefollowing method. First, a solvent for adjusting the viscosity is addedinto a mixture including the inorganic filler and the thermosettingresin composition so as to prepare a slurry having a desired slurryviscosity. An example of the solvent for adjusting the viscosityincludes, for example, methyl ethyl ketone, toluene, and the like.

Then, the slurry is formed into a film on a preliminarily prepared moldrelease film by a doctor blade method, etc. and the film is treated at atemperature below the curing temperature of the thermosetting resin soas to volatilize the solvent for adjusting the viscosity. Thereafter,the mold release film is removed so as to produce a base material sheet.

The thickness of the film at the formation is appropriately determinedby the amount of the solvent for adjusting viscosity to be added.Usually the thickness ranges from 80 to 200 μm. Furthermore, theconditions for volatilizing the solvent for adjusting viscosity areappropriately determined in accordance with the kinds of solvents foradjusting viscosity, kinds of thermosetting resins, or the like.However, usually, the volatilization is carried out at a temperature of70 to 150° C. for 5 to 15 minutes.

As the mold release film, usually, an organic film can be used. Forexample, it is preferable to use an organic film containing at least oneresin selected from the group consisting of, for example, polyethylene,polyethylene terephthalate, polyethylene naphthalate, polyphenylenesulfide (PPS), polyphenylene terephthalate, polyimide and polyamide, andmore preferably PPS.

Furthermore, another example of the base material sheet includes areinforcer sheet impregnated with a thermosetting resin composition, andhaving at least one through hole filled with a conductive paste.

The reinforcer sheet is not particularly limited as long as it is aporous material capable of holding the thermosetting resin. However, itis preferable that the reinforcer sheet is at least one selected fromthe group consisting of a glass fiber woven fabric, a glass fibernon-woven fabric, a woven fabric of a thermal resistant organic fiberand a non-woven fabric of a thermal resistant organic fiber. An exampleof the thermal resistant organic fiber includes, for example, allaromatic polyamide (aramide resin), all aromatic polyester, polybutyleneoxide, and the like. In particular, aramide resin is preferable. Anotherexample of the base material sheet includes a film of polyimide etc. Byusing the film of polyimide etc., an excellent substrate having a finepattern of wiring and via conductor can be obtained.

The thermosetting resin is not particularly limited. However, it ispreferable that a resin contains at least one selected from the groupconsisting of an epoxy resin, a phenol resin, a cyanate resin and apolyphenylene phthalate resin because of its excellent thermalconductivity. Furthermore, the thermosetting resin can be used singly orby combination of two kinds or more of the thermosetting resins.

Such a base material sheet can be produced, for example, by immersingthe reinforcer sheet into the thermosetting resin composition, and thendrying to a half-cured state. It is preferable that the immersion iscarried out so that the rate of the thermosetting resin with respect tothe base material sheet is 30 to 60 weight %.

In the method for producing the multi-layered wiring substrate, it ispreferable that when the base material sheet containing a thermosettingresin is used, the wiring substrates are laminated by a heating andpressing treatment so as to cure the thermosetting resin. This can beperformed sufficiently at a low temperature such as 200° C., i.e., thecuring temperature of the thermosetting resin.

Furthermore, another base material sheet includes a green sheetcontaining an organic binder, plasticizer, and ceramic powder, having atleast one through hole filled with a conductive paste. This basematerial sheet exhibits an excellent thermal resistance and thermalconductivity.

The ceramic powder preferably contains at least one ceramic selectedfrom the group consisting of Al₂O₃, MgO, ZrO₂, TiO₂, BeO, BN, SiO₂, CaOand glass. More preferably, the ceramic powder is a mixture of 50 to 55weight % of Al₂O₃ and 45 to 50 weight % of glass power. Moreover, theceramic can be used singly or in combination of two kinds or more ofthem.

An example of the binders to be used includes, for example, polyvinylbutyrate (PVB), acrylic resin, methyl cellulose resin, and the like. Anexample of the plasticizer includes, for example, butyl benzyl phthalate(BBP), dibutylphthalate (DBP), and the like.

Such a green sheet containing the ceramic powder can be produced by, forexample, the same method as the method for producing the base materialsheet including the inorganic filler and the thermosetting resin.Moreover, the treating conditions are appropriately determined by thekinds of the component materials, etc.

It is preferable in the method for producing the multi-layered wiringpattern that when the green sheet is used for the base material sheet,the wiring substrates are laminated by heating and pressing the basematerials to be adhered and by sintering the ceramic powder by firing.

The thickness of the base material sheet is usually 30 to 250 μm.

It is preferable that the base material sheet has at least one throughhole and the through hole is filled with a conductive paste. Theposition of the through hole is not particularly limited as long as thethrough hole is formed so that it is in contact with the wiring pattern.However, it is preferable that through holes are positioned by equalintervals of 250 to 500 μm pitch.

The size of the through hole is not particularly limited. However, thediameter of the through hole is 100 to 200 μm, and preferably 100 to 150μm.

The method for forming through holes is appropriately determined inaccordance with the kinds of the base material sheet, etc. However, thepreferable example of the method includes, for example, a carbon dioxidegas laser process, a process with a punching machine, a bulk processwith a mold, etc.

The conductive paste is not particularly limited as long it hasconductivity. However, usually, a resin containing a particulateconductive metal, and the like, can be used. An example of theconductive metal material to be used includes, for example, copper,silver, gold, silver-palladium, and the like. An example of thethermosetting resin includes, for example, an epoxy resin, a phenolresin, an acrylic resin, and the like. The amount of the conductivemetal material in the conductive paste is usually 80 to 95 weight %.Furthermore, when the base material sheet is a green sheet, glass and anacrylic binder are used instead of thermosetting resin.

Next, the method for adhering the transfer material to the base materialsheet in the step (h) and the method for peeling off the first metallayer from the second metal layer in the step (i) are not particularlylimited. However, when the base material sheet includes a thermosettingresin, for example, the adhering method and the peeling method can becarried out as follows.

First, the transfer material and the base material sheet are placed asmentioned above, and heated and pressed so as to fuse and soften thethermosetting resin in the base material sheet, thus allowing the metallayer (the second metal layer, etc.) that forms the wiring pattern to beembedded in the base material sheet. Then, it is treated at a softeningtemperature or a curing temperature of the thermosetting resin. In thelatter case, the resin is cured. This allows the transfer material andthe base material sheet to be adhered and the adhesion between thesecond metal layer and the base material sheet to be fixed.

The conditions for heating and pressing treatment is not particularlylimited as long as the thermosetting resin is not perfectly cured.However, the heating and pressing usually can be carried out under thepressure of 9.8×10⁵ to 9.8×10⁶ Pa (10 to 100 kgf/cm²), at thetemperature of 70 to 260° C. for 30 to 120 minutes.

Then, after the transfer material and the sheet substrate are adhered toeach other, for example, the first metal layer that is the carrier layeris pulled so as to peel it off in the peel layer. Thereby, the firstmetal layer can be peeled off from the second metal layer. Namely, sincethe adhesive strength between the first metal layer and the second metallayer via the peel layer is weaker than the adhesive strength betweenthe base material sheet and the second metal layer that is a wiringlayer, the adhering surface between the first metal layer and the secondmetal layer is peeled off, and only the second metal layer istransferred to the base material sheet while the first metal layer ispeeled off. Curing of the thermosetting resin may be carried out afterthe first metal layer is peeled off from the second metal layer.

When the base material sheet is the green sheet including a ceramic, forexample, the adhering method and peeling method can be carried out asfollows. The transfer material and the base material sheet are heatedand pressed as mentioned above so as to allow the metal layer forforming the wiring pattern to be embedded into the base material sheet,thus adhering the base material sheet to the transfer material.Thereafter, similar to the above, forming materials of the transfermaterial except the wiring layer (second metal layer, etc.) are removedby peeling. Then, a constraint sheet is placed and laminated on one orboth surfaces of the green sheet onto which the second metal layerforming the wiring pattern is transferred. The constraint sheet includesan inorganic composition that substantially is not sintered nor shrunkat the firing temperature of the green sheet. Thereafter, the binderremoving process and firing are carried out. Furthermore, thereafter theconstraint sheet is removed, and thus a ceramic substrate including thewiring pattern formed of the second metal layer etc. can be formed.

The conditions for heating and pressing when the transfer is carried outare appropriately determined in accordance with the kinds of thethermosetting resin contained in the green sheet and conductive paste.However, usually, the heating and pressing treatment is carried outunder the pressure of 9.8×10⁵ to 1.96×10⁷ Pa (10 to 200 kgf/cm²), at atemperature of 70 to 100° C. for 2 to 30 minutes. Therefore, the wiringpattern can be formed without damaging the green sheet.

The heating and pressing conditions for placing and laminating theconstraint sheet including an inorganic composition that substantiallyis not sintered nor shrunk at the firing temperature of the green sheetis appropriately determined in accordance with the kinds of thethermosetting resin contained in the green sheet and the constraintsheet. However, usually, the conditions include a pressure of 1.96×10⁶to 1.96×10⁷ Pa (20 to 200 kgf/cm²), at a temperature of 70 to 100° C.for 1 to 10 minutes.

The conditions for the treatment for removing the binder areappropriately determined in accordance with the kinds of binders, metalthat forms the wiring pattern, or the like. However, usually, thetreatment is carried out by the use of the electric furnace at atemperature of 500 to 700° C., with temperature rising time of 10 hours,and maintaining time of 2 to 5 hours. In particular, in the case of thecopper foil wiring pattern, a green sheet formed of an organic bindersuch as methacrylic methacrylic that is excellent in thermal deformationproperty is used, and the binder removing process and firing are carriedout in an atmosphere of nitrogen, that is, an atmosphere ofnon-oxidation.

The conditions for firing are appropriately determined in accordancewith the kinds of the ceramic and the like. However, usually, the firingis carried out in a belt furnace, at a temperature of 860 to 950° C. for30 to 60 minutes in the air or an atmosphere of nitrogen.

Herein, the second production method is described. When themulti-layered substrate is produced in this method, each single layerwiring substrate that is produced by the above-mentioned method islaminated and the interlayer portion is adhered. Moreover, after aplurality of single layer substrates are laminated, the whole portioncan be adhered and fixed.

For example, when a multi-layered wiring substrate produced by the useof a base material sheets including a thermosetting resin are laminated,first, similar to the above, only the wiring layer (second metal layeretc.) is transferred to the base material sheet from the transfermaterial so as to form a single layered wiring substrate by a heatingand pressing treatment. When this wiring substrate is formed, thethermosetting resin is not subjected to the curing treatment and keptuncured. The plurality of single layer substrates are prepared andlaminated. Then, this laminate is heated and pressed at a curingtemperature of the thermosetting resin so as to cure the thermosettingresin, thereby adhering and fixing the place between the wiringsubstrates. When the heating and pressing temperature for transferringthe wiring layer in the single layer wiring substrate is set to be 100°C. or less, intentionally, even after the transfer, the base materialsheet can be used as a prepreg. Thus, it is possible to produce amulti-layered wiring substrate by adhering and fixing the laminate afterthe single layer wiring substrates are laminated instead of sequentiallylaminating the single layer wiring substrates.

With the use of the transfer material of the present invention, abuild-up substrate having a glass-epoxy substrate etc. as a core layercan be produced by a method in which a wiring pattern is transferred toan uncured base material sheet to form it into single layered wiringsubstrates, and these single layered wiring substrates are sequentiallylaminated as in an uncured state, and the laminated substrates are curedas a whole.

Furthermore, for example, when a multi-layered substrate is produced bylaminating ceramic wiring substrates using a base material sheetincluding a ceramic, as mentioned above, after the transfer material ispressed onto the base material sheet so as to transfer only the wiringlayer (second metal layer etc), a plurality of the single layeredceramic wiring substrates are laminated and heating and pressingtreatment and firing of the ceramic are carried out. Thus, the placebetween the wiring substrates are adhered and fixed.

The number of the laminated layers in the multi-layered wiringsubstrates is not particularly limited. However, the number is usually 4to 10 layers, and as many as 20 layers is also possible. Furthermore,the total thickness of the multi-layered wiring substrate is usually 200to 1000 μm.

The wiring substrate forming the outermost layer of the multi-layeredwiring substrate is excellent in electric connection. Therefore, asmentioned above, the wiring substrate forming the outermost layerpreferably has a structure in which a wiring layer (second metal layeretc.) is embedded in the concave portion of the surface thereof by theuse of the transfer material of the present invention (first, second orthird transfer material). Furthermore, middle layer(s) other than theoutermost layer of the multi-layered wiring substrate may be a flatstructure or may have a wiring layer (second metal layer, etc.) formedon the concave portion of the surface.

Hereinafter, a configuration of the wiring substrate of the presentinvention will be described in detail.

FIG. 8 shows a wiring substrate of a first embodiment produced by usingthe transfer material of the present invention (first, second, or thirdtransfer material). The wiring substrate of the first embodimentincludes a wiring pattern 801 formed on a base material sheet 805. Atleast one surface of the base material sheet 805 is provided with atleast one concave portion on the bottom of which the wiring pattern 801is formed. Furthermore, on the wiring pattern 801, a plating layer 802of gold etc. is formed by a plating treatment.

According to this configuration, when a semiconductor is flip-chipmounted on the wiring substrate, as shown in FIG. 9, the concave portioncan be used for the positioning of a bump 904 formed on a semiconductor905. Since a connection portion 903 between the semiconductor 905 andthe substrate is formed on the chemically stable gold plating etc., thecontacting resistance becomes smaller and the reliability can beimproved. Furthermore, since the plating treatment is carried out by theuse of the concave portion, it is possible to secure a creepingdistance, thus maintaining the reliability of the fine wiring patternwithout occurrence of the short circuit etc.

It is preferable in the wiring substrate that the thickness of thewiring pattern layer/patterns is 3 to 35 μm. When the thickness is lessthan 3 μm, excellent conductivity may not be obtained. On the otherhand, when the thickness is more than 35 μm, it may be difficult to forma fine wiring pattern.

It is preferable in the wiring substrate that the depth of the concaveportion is 1 to 12 μm. When the depth is more than 12 μm, for example,when a semiconductor is mounted, some bumps may not be brought intocontact with the wiring pattern or it may take a long time to seal witha sealing resin. On the other hand, when the depth is less than 1 μm,the concave portion may not serve for the positioning of the bumps.

The second embodiment of the wiring substrate formed by the transfermaterial of the present invention is a multi-layered wiring substrate inwhich, as shown in FIG. 10J, a wiring pattern (1002 etc.) is formed onthe base material sheet 1001, at least one surface of the substrate hasat least one concave portion and the wiring pattern is formed on thebottom portion of the concave portion. In this multi-layered wiringsubstrate, by using the transfer material of the present invention, thewiring pattern can be formed on the base material sheet that is anuncured base material sheet or a green sheet. Thus, after the singlelayered substrate is laminated, an entire laminate is adhered and fixed,and a base material sheet and metal foil wiring patterns can be curedsimultaneously. As a result, a multi-layered wiring substrate includingan interlayer via of each layer having a high position accuracy can beobtained.

The third embodiment of the wiring substrate formed by the transfermaterial of the present invention is a multi-layered wiring substratehaving a laminate structure, as shown in FIG. 11. The laminate structureincludes an electrically insulating substrate 1608 formed of a ceramic,and an electrically insulating substrate 1602 including at least athermosetting resin composition. The electrically insulating substrate1608 formed of a ceramic is formed in a state in which a wiring patternis prevented from projecting from the surface by using the transfermaterial of the present invention. Furthermore, it is possible tolaminate the electrically insulating sheet containing an uncuredthermosetting resin and electrically insulating substrate formed of aceramic and to cure them at relatively small pressure in one time. Thus,it is possible to attain the multi-layered substrate without damagingthe ceramic layer.

On the other hand, the multi-layered wiring substrate can be produced byadhering it to an electrically insulating sheet containing athermosetting resin after the wiring pattern has been formed beforehandon the ceramic substrate by a printing method or firing. However, sincethe wiring pattern produced by a printing method becomes a projection,in the process of adhering the wiring pattern to the electric insulatingsheet containing a thermosetting resin composition, stress concentrationoccurs, from which cracks are generated in the ceramic substrate layer.

The fourth embodiment of the wiring substrate produced by using thetransfer material of the present invention is a multi-layered wiringsubstrate including an electrically insulating substrate 1608 formed ofa ceramic, and an electrically insulating substrate 1602 including atleast a thermosetting resin composition, similar to the wiring substrateof the third embodiment, as shown in FIG. 12. Furthermore, an interlayervia hole 1603 filled with a conductive via composition is provided inthe predetermined position of each layer of the laminated electricinsulating substrates, and a wring pattern 1610 electrically connectedto the via holes 1608 is formed. Although this structure is a laminateof the ceramic substrate and a resin substrate, a multi-layered wiringconnection can be used that is the same as in the wiring rule of themulti-layered wiring substrate formed of only ceramic substrates or amulti-layered wiring substrate formed of only resin substrates.

In this case, as the conductive resin composition used for theinterlayer connection via of the ceramic substrates, a sintered bodyformed of metal powder and glass powder is used. On the other hand, asthe conductive resin composition used of the inter connection via of theresin substrate, a resin composition made of a mixture of metal powderand the thermosetting resin is used.

Furthermore, in the interface between the electrically insulatingsubstrate containing a thermosetting resin composition and the ceramicsubstrate, the wiring pattern layer formed on the ceramic substrate isnot projected from the surface and is incorporated in the ceramicsubstrate.

Furthermore, it is preferable in the firing process of the ceramicsubstrate that the firing treatment is carried out after the constraintsheet including an inorganic composition that substantially is notsintered nor shrunk at the firing temperature of the green sheet isplaced on both surfaces or one surface of the green sheet on which awiring pattern is transferred. Thus, since the non-shrinkage sinteringin the plane direction can be realized, when laminating to the resinbase substrate, the common interlayer via positional data can beemployed.

Needless to say, after the wiring pattern may be formed on the ceramicgreen sheet filled with the via paste by a printing method and bysintering, this is adhered to the electrically insulating sheetcontaining a thermosetting resin composition so as to form a interlayerconnection. However, since the wiring pattern by a printing methodbecomes a projection, in a process of adhering the electricallyinsulating sheet containing the thermosetting resin composition to theceramic green sheet, stress concentration occurs, from which cracks aregenerated in the ceramic substrate layer.

Furthermore, as shown in FIG. 13, by using the transfer material of thepresent invention, it is possible to produce a multi-layered wiringsubstrate in which a low resistance wiring is formed. The low resistancewiring is produced by laminating a ceramic substrate 1708 formed of analumina substrate having a relatively high mechanical strength, and analuminum nitride substrate having a high thermal conductivity, or thelike, onto an electrically insulating substrate 1702 containing at leasta thermosetting resin composition. Herein, both an interlayer viaconductor used for the ceramic substrate and an interlayer via conductorused for the resin based substrate are formed of the same thermosettingresin composition.

Needless to say, as the ceramic substrate used herein, a low temperaturesintering ceramic capable of being sintered together with copper,silver, etc, for example, alumina glass ceramic, Bi—Ca—Nb—O basedceramic, and the like, may be used.

The fifth embodiment of the wiring substrate formed by the use of thetransfer material of the present invention is a dissimilar laminatewiring substrate. As shown in FIG. 14, similar to the wiring substrateof the third or fourth embodiment, the dissimilar laminate wiringsubstrate has a laminate structure including an electric insulatingsubstrate containing a thermosetting resin composition and anelectrically insulating substrate containing a ceramic. In thisembodiment, electrically insulating substrates 1801 and 1802 formed ofdifferent kinds of ceramics each having a different composition arelaminated via the electrically insulating substrate 1807 including athermosetting resin.

According to this structure, it is possible to obtain a dissimilarlaminate between a magnetic ceramic and a dielectric ceramic or adissimilar laminate between a dielectric ceramic having a highdielectric constant and a dielectric ceramic having a low dielectricconstant, which conventionally has been technically difficult to achievebecause of the difference in the firing temperatures or shrinkage rate,or mutual diffusion etc. at the time of sintering. Furthermore, in themethod for producing the dissimilar laminate wiring pattern substrate ofthe present invention, each wiring substrate is produced by transferringa wiring pattern such as a copper foil etc. to the green sheet oruncured thermosetting resin impregnated sheet. Thus, a laminate having alow resistant wiring in all layers can be obtained without being damagedat the time of laminate.

According to the wiring substrate according to the fifth embodiment, byinterposing the electric insulating substrate including a thermosettingresin composition between the ceramic substrates, it is possible tolaminate ceramic substrates, each having a different sinteringtemperature. Thus, it is possible to produce easily, for example, adissimilar laminate wiring substrate in which each layer has differentdielectric constant or a dissimilar laminate wiring substrate in which amagnetic layer and dielectric layer are laminated.

Needless to say, after a wiring pattern is formed on a ceramic greensheet filled with via paste by a printing method and by firing, then theelectrically insulating sheet containing a thermosetting resincomposition may be laminated onto the ceramic green sheet. However,since the wiring pattern by a printing method becomes a projection, inthe process of adhering the wiring pattern to electrically insulatingsheet containing a thermosetting resin composition, stress concentrationoccurs, from which cracks are generated in the ceramic substrate layer.

The sixth embodiment of the wiring substrate formed by the use of thetransfer material of the present invention is a laminated structure. Asshown in FIG. 15, similar to the wiring substrate of the third or fourthembodiment, a laminated structure includes electric insulatingsubstrates 1801 and 1802 formed of a ceramic and an electric insulatingsubstrate 1807 formed of at least one thermosetting resin composition.And the electric insulating substrate 1807 including a thermosettingresin is formed on at least a top layer or a bottom layer, and theelectric insulating substrates 1801 and 1802 including a ceramic areformed in inside layers. According to this structure, since the layercovering the outermost surface of the substrate is formed of thethermosetting resin composition that is not likely to be cracked, it isexcellent in falling resistant property.

In the production method for producing these dissimilar wiringsubstrates, by transferring the wiring pattern such as a copper foil,etc. to a green sheet or an uncured thermosetting resin impregnatedsheet, each wiring substrate is produced. Thus, a laminate having a lowresistance wiring in all layers can be obtained without being damaged atthe time of laminate.

Needless to say, after a wiring pattern is formed on a ceramic greensheet filled with via paste by a printing method or firing, then anelectrically insulating sheet containing a thermosetting resincomposition may be laminated onto the ceramic green sheet, therebyperforming an interlayer connection of the laminate. However, since thewiring pattern formed by a printing method becomes a projection, in aprocess of adhering the wiring pattern to the electrically insulatingsheet containing a thermosetting resin composition, stress concentrationoccurs, from which cracks are generated in the ceramic substrate layer.

Moreover, it is also possible to form circuit components such as aninductor, a capacitor, a resistor, a semiconductor device, or the like,with electrically connected to the wiring pattern of the transfermaterial of this embodiment and to transfer them to the substratetogether with the wiring pattern. It is preferable that the passivecomponents such as inductor, capacitor, and resistor, etc. are formed onthe substrate by a printing method, for example a screen printingmethod.

Next, the further specific Examples of the first to fourth embodimentsare explained hereinafter.

Example 1

A first transfer material of the present invention was produced by aprocess shown in FIG. 4A to 4F.

As shown in FIG. 4A, an electrolytic copper foil having a thickness of35 μm was prepared as a first metal layer 401. First, a copper salt rawmaterial was dissolved in an alkaline bath and allowed to beelectrodeposited on a rotation drum so that it had a high electriccurrent density. Thus, a metal layer (copper layer) was formed and thiscopper layer was rolled up continuously so as to form an electrolyticcopper foil.

Next, as shown in FIG. 4B, a Ni—P alloy layer was formed in a thicknessof about 100 nm as a peel layer 402 on the surface of the first metallayer 401 by plating. The electrolytic copper foil same as the firstmetal layer 401 was laminated thereon in a thickness of 9 μm as a secondmetal layer for forming wiring pattern 403 by electrolytic plating.Thus, a three-layered structure laminate was produced.

The surface of the laminate was subjected to a roughening treatment sothat the average roughness (Ra) of the center line of the surface wasabout 4 μm. The roughening treatment was carried out by precipitatingfine copper powder on the electrolytic copper foil.

Next, as shown in FIGS. 4C to 4E, a dry film resist (DFR) 404 was placedby a photolithography method, and exposure and development of the wiringpattern portion was carried out. The first metal layer 403, the peellayer 402 and the surface portion of the first metal layer 401 of thelaminate were etched by a chemical etching process (immersing in anaqueous solution of ferric chloride) so as to form a desired wiringpattern.

Thereafter, as shown in FIG. 4F, the first transfer material wasobtained by removing a mask portion (DFR 404) with a peeling material.Since the first metal layer and the second metal layer are formed of thesame materials, not only the second metal layer but also the surfacelayer of the first metal layer can be etched in a wiring pattern in oneetching process. This first transfer material has a structural featurein that the surface layer portion of the first metal layer that is acarrier layer is also processed in the wiring pattern.

In the produced first transfer material, the peel layer 402 adhering thefirst metal layer 401 and the second metal layer 403 is weak in adhesivestrength itself but excellent in etch resistance property. Thus, even ifthe entire laminate of the first metal layer 401, the peel layer 402,and the second metal layer 403 are subjected to the etching process,interlayer portions are not peeled off and the wiring pattern can beformed without problems. On the other hand, the adhesive strengthbetween the first metal layer 401 and the second metal layer 403 was 40N/m (gf/cm), exhibiting an excellent peeling property. When the secondmetal layer 403 was transferred to the substrate by using such a firsttransfer material, the adhesive plane between the second metal layer 403and the peel layer 402 was peeled off easily, so that only the secondmetal layer 403 was transferred to the substrate.

Since the first transfer material according to the present inventionincludes a carrier (first metal layer) formed of a copper foil having athickness of 35 μm, even if the transfer material is deformed at thetime of transfer, the carrier layer was resistant to the deformationstress.

In the first transfer material of the first metal layer that is acarrier layer, the wiring pattern is a convex portion and the portionexcluding the wiring pattern is a concave portion. Therefore, when thetransfer material is pressed onto the base material sheet (material forthe substrate), the base material extruded from the portion into whichthe wiring pattern is embedded is likely to flow into the concaveportion, thus suppressing the deformation stress that distorts thepattern in the vertical direction. Therefore, the distortion of thepattern in this Example was only the amount generated by the curing andshrinking of the base material (0.08%).

As a comparative example, by using a transfer material on which thesurface layer of the first metal layer 401 is not etched at all and onlythe second metal layer is formed into the wiring pattern (that is, atransfer material including a carrier layer having a flat surface), thewiring layer was transferred to the base material sheet. The distortionof the wiring pattern was at most 0.16%. In this comparative example,since the carrier is a thick copper foil, basically the distortion issmall as in Example 1. However, it was confirmed that in the portion inwhich the wiring patterns are concentrated, the wiring pattern issomewhat distorted because the concave portion into which base materialflows is small. The distortion amount of the pattern is substantiallysmall. However, when the transfer material according to the comparativeexample is used, unlike the first transfer material of the presentinvention, a surface of the wiring pattern is on the same plane orconvex shape with respect to the surface of the substrate, but is notconcave. Therefore, the effect of facilitating the positioning at thetime of flip chip mounting of the transfer material of the presentinvention cannot be exhibited. This shows the effect of the transfermaterial of the present invention in which the convex portioncorresponding to the wiring pattern is formed on the surface of thecarrier layer by etching also the first metal layer that is a carrierlayer.

In Example 1, for example, a Ni-plating layer, a nickel-phosphorousalloy layer, an aluminum plating layer, or the like, having a thicknessof 200 nm or less, is used as the peel layer. However, the peel layer isnot necessarily limited thereto, and any organic layers can be used. Anexample of the organic layer includes, for example, a long chainaliphatic carboxylic acid that can be bonded to, for example, Cu andthat is in a solid state at room temperature. By using this, the sameeffect as the transfer material of this example can be realized.

Example 2

A second transfer material of the present invention was produced by aprocess shown in FIGS. 5A to 5E by a production method different fromExample 1. The second transfer material is different from the firsttransfer material according to Example 1 in the structure of the firsttransfer material and the wiring layer.

First, an electrolytic copper foil having a thickness of 35 μm wasprepared as a first metal layer 501. A copper salt raw material wasdissolved in an alkaline bath and allowed to be electrodeposited to arotation drum so that it had a high electric current density. Thus, ametal layer (copper layer) was formed and this copper layer was rolledup continuously so as to form an electrolytic copper foil.

Next, a peel layer 502 formed of a thin nickel plating layer was formedin a thickness of 100 nm or less on the surface of the first metal layer501 formed of the electrolytic copper foil. The electrolytic copper foilthat is the same as the first metal layer 501 was laminated thereon in athickness of 3 μm as a second metal layer for forming wiring pattern 503by electrolytic plating. Thus, a three-layered laminate including thefirst metal layer 501, the peel layer 502 and the second metal layer 503was produced.

The surface of the second metal layer 503 of the laminate was subjectedto a roughening treatment, so that the average roughness (Ra) of thecenter line of the surface was about 3 μm. The roughening treatment wascarried out by precipitating fine copper powder on the electrolyticcopper foil. Furthermore, an adhesive material (not shown) was coatedand a dry film resist (DFR) 504 used for the photolithography was placedthereon. The DFR 504 has a plating resistant property and serves as aplating resist. With the above-mentioned process, a laminate shown inFIG. 5A was produced.

Next, as shown in FIG. 5B, the DFR 504 of the wiring pattern was exposedand developed so as to form a concave portion reaching the second metallayer 503 in a wiring pattern region of the DFR 504. The depth of theconcave portion was 25 μm. Thereafter, as shown in FIG. 5C, a thirdmetal layer 505 was formed of a copper plating layer having a thicknessof 20 μm in the concave portion by plating with an electrolytic copper;and then the laminate was immersed in the peeling solution so as toremove the DFR 504.

Finally, as shown in FIG. 5E, the patterning was carried out by achemical etching process by immersing the laminate in an aqueoussolution of ferric chloride. This etching process was carried out inorder to remove the thin second metal layer 503 having a thickness of 3μm and peel layer 502 (plating layer). As a result, the etching processwas carried out for a short time, also the third metal layer 505 waspartially etched so as to have a thickness of about 15 μm, andfurthermore, the surface of the first metal layer 501 also was erodedpartially. Thus, as shown in FIG. 5E, the second transfer material wasproduced.

Since the first, second and third metal layers are formed of the samematerials, i.e., copper, not only the second and third metal layers butalso a part of the first metal layer can be removed by one etchingprocess. Thus, a part excluding the wiring pattern on the surfaceportion of the first metal layer was formed into a concave portion.Furthermore, similar to Example 1, since the surface of the first layer,i.e. a carrier layer, was etched, and the third metal layer was formedby an additive method, the thickness can be controlled arbitrarily.Furthermore, in Example 2, the peel layer is not limited to a platinglayer, and an extremely thin adhesive layer formed of an organic layeror a sticking agent layer may be employed.

In the thus produced second transfer material, the peel layer 502 forconnecting the first metal layer 501 to the metal layers 503 and 505 forforming the wiring patterns is weak in adhesive strength itself butexcellent in etch resistance property. Thus, even if the four-layerstructured entire laminate shown in FIG. 5D is subjected to an etchingprocess, interlayer portions are not peeled off and the wiring patterncan be formed without problems.

On the other hand, the adhesive strength between the first metal layer501 and the second metal layer 503 via the peel layer 502 is 30 N/m(gf/cm), exhibiting an excellent peeling property. Thereby, with thissecond transfer, after the second metal layer 503 as the wiring pattern,and the third metal layer 505 are transferred to the base material sheet(a material for the substrate), the portion between the second metallayer 503 and the peel layer can be peeled off easily with only thewiring layer remained on the substrate. At this time, the peel layerformed of the peel layer 502 was attached to the side of the first metallayer 501, that is, a carrier.

Moreover, as shown in FIG. 5E, the produced second transfer material ofthis embodiment is pressed onto the base material sheet (a material forthe substrate) including an uncured thermosetting resin and thermallycured, then the first metal layer is removed by a chemical etchingprocess, and thereby the wiring layer (the second metal layer 503 andthe third metal layer 505) may be transferred to the substrate. Bycontrolling the etching time, it is possible to make the substratesurface including the wiring layer flat and to make the wiring layer aconcave shape with respect to the substrate surface.

In this Example, similar to Example 1, the carrier layer is formed ofcopper foil having a thickness of 35 μm, even if the base material wasdeformed at the time of transfer, the carrier layer was resistant to thedeformation stress. On the other hand, in the transfer material inExample 2, the concave portion of the first metal layer, that is, acarrier layer is secured to be as deep as 5 μm. This allows the basematerial of the portion into which the wiring layer is embedded to flowtoward the concave portion easily when the transfer material is pressedonto the base material sheet and to suppress the deformation stress thatdistorts the pattern in the vertical direction.

Therefore, when the transfer material according to this Example wasused, the distortion of the pattern in this Example was only the amountgenerated by the curing and shrinking of the base material (0.08%). Thisshows the effect that the surface portion of the first metal layer thatis a carrier layer is etched so as to form the wiring pattern to be aconvex shape and to form the portion excluding the wiring pattern to bea concave portion. Furthermore, when the wiring resistance aftertransfer was measured, as compared with Example 1, a cross sectionalarea for the wiring can be increased and reduce the resistance value byabout 20 to 30% because the thickness of the wiring pattern wasincreased by the third metal layer.

In this Example, as shown in FIG. 5E, after the patterning of the firstmetal layer was carried out by a chemical etching process, transfer wascarried out. However, the transfer may be carried out with curing thebase material by using the transfer material without chemical etchingprocess. However, in this case, after the transfer, the peeling layerand the first metal layer are peeled off, and then the second metallayer is removed by a soft etching process etc., and thus the wiringpattern including only a third metal layer can be formed.

Furthermore, also in this case, the carrier copper foil (first metalfoil) including a convex wiring pattern can be reused after transfer.Furthermore, the wiring pattern transferred to the substrate by usingthe transfer material of this Example has a concave portion with respectto the substrate surface. This concave portion can be used forpositioning, e.g. facilitates the flip-chip mounting of a bare chip.

Example 3

A transfer material according to this Example is another example of thesecond transfer material. The transfer material of this Example isdifferent from that of Example 2 in the structure of the wiring layer,however, the drawing is the same, and the transfer material of thisExample is described with reference to FIGS. 5A to 5E.

First, an electrolytic copper foil having a thickness of about 35 μm wasprepared as a first metal layer 501. A copper salt raw material wasdissolved in an alkaline bath and allowed to be electrodeposited on arotation drum so that it had a high electric current density. Thus, ametal layer (copper layer) was formed. This copper layer was rolled upcontinuously so as to form an electrolytic copper foil.

Next, a peel layer 502 formed of a thin nickel plating layer having athickness of 100 nm or less was formed on the surface of the first metallayer 501. The electrolytic copper foil same as the first metal layer501 was laminated thereon in a thickness of 3 μm as a second metal layerfor forming wiring pattern 503 by electrolytic plating. Thus, athree-layered laminate including the first metal layer 501, the peellayer 502 and the second metal layer 503 was produced.

The surface of the laminate was subjected to a roughening treatment sothat the average roughness (Ra) of the center line of the surface wasabout 3 μm. The roughening treatment was carried out by precipitatingfine copper powder on the electrolytic copper foil. Furthermore, anadhesive material that was the same as in Example 2 was coated and a dryfilm resist (DFR) 504 used for the photolithography was placed thereon.The DFR 504 has a plating resistant property and serves as a platingresist. Thus, as shown in FIG. 5A, a four-layered laminate was produced.

Next, as shown in FIG. 5B, the DFR 504 of the wiring pattern was exposedand developed so as to form a concave portion that reaches the secondmetal layer 503 in a region corresponding to the wiring pattern in theDFR 504. The depth of the concave portion is 25 μm. Thereafter, as shownin FIG. 5C, a third metal layer 505 formed of a copper plating layerhaving a thickness of 2 μm was formed. Then, as shown in FIG. 5D, thelaminate was immersed in a peeling solution so as to remove the DFR 504.

Finally, as shown in FIG. 5E, the patterning was carried out by achemical etching process by immersing the laminate in an aqueoussolution of ferric chloride. This etching process is different from thatof Example 2 in that a gold plating layer 505 serves as an etchingresist, so that it is possible to remove selectively the thin secondmetal layer 503 having a thickness of 3 μm and the thin peel layer 502.As a result, since a transfer material whose top layer is gold platedwas obtained, the surface of the wiring pattern may not be oxidized.Therefore, when a bare chip or a component is mounted on the wiringpattern after the wiring pattern is formed on the substrate by using thetransfer material, it is possible to attain a low resistance connection.

Furthermore, as a comparative example, a gold plated transfer materialwas produced by plating gold on the entire surface of the transfermaterial having a wiring formed of single layered copper foil wiring, asshown in FIG. 1. When the gold plated transfer material was examined fortransferring property, the transferring property of the wiring patternwas damaged. This shows the effect of the transfer of this Example onwhich a gold plating layer is formed only on the surface layer of thewiring pattern.

Example 4

A third transfer material of the present invention was produced as shownin FIGS. 6A to 6E. The third transfer material is the same at the secondtransfer material according to Example 2 or 3 of the present inventionexcept the structure of the wiring layer.

First, as shown in FIG. 6A, a four-layered laminate including a firstmetal layer 601, a peel layer 602, a second metal layer 603 and dry filmresist (DFR) 604 was prepared. Since the structure and the method forproducing this laminate are the same as the laminate shown in FIG. 4C inExample 1, the explanation is not repeated herein.

Next, as shown in FIG. 6B, a region 607 excluding a region correspondingto the wiring pattern in the DFR 604 was exposed and developed so as toform a concave portion 608 having a thickness of 25 μm corresponding tothe thickness of the DFR 604 was formed in the region of the wiringpattern. Thereafter, as shown in FIG. 6C, a copper plated layer (thirdmetal layer) 605 having a thickness of 15 μm was formed by electrolesscopper plating in a deposition thickness of about 2 μm followed byelectrolytic copper plating. In this Example, further a silver platinglayer (fourth metal layer 606) was deposited thereon by electrolyticsilver plating to a thickness of about 3 μm.

Next, similar to Example 2, as shown in FIG. 6D, the laminate wasimmersed in a peeling solution so as to remove the DFR. Finally, asshown in FIG. 6E, the patterning was carried out by a chemical etchingprocess by immersing the laminate in an aqueous solution of ferricchloride. This etching process was carried out basically in order toremove the thin second metal layer 603 having a thickness of 3 μm.However, since the fourth metal layer 606 that is a silver plating layerserves as an etching mask, the third metal layer 605 and the fourthmetal layer 606 are not substantially etched except for a small sideetching portion, so that the thickness is maintained. Furthermore, thisetching process is continued until the peel layer 602 and the surfaceportion of the first metal layer 601 were corroded.

Also in this Example, short-time etching is sufficient for thepatterning of the second metal layer 603, etc. Thus, the third transfermaterial was obtained, in which a region excluding the wiring pattern onthe surface layer portion of the first metal layer 601 was formed in aconcave shape. By adjusting the etching time, it is possible to controlthe depth of the concave portion of the first metal layer 601 freely.

Since the first, second and third metal layers are formed of the samematerial, copper, not only the second and third metal layers but also apart of the first metal layer is corroded by one chemical etchingprocess. Thus, a part excluding the wiring pattern on the surface layerportion of the first metal layer could be formed into a concave portion.Furthermore, similar to Example 1, in the third transfer materialaccording to this Example, the surface of the first layer that is acarrier layer was etched. The fourth metal layer (silver plating layer)that is different from the second and third metal layers (copper platinglayers) is further formed by an additive method.

In the thus produced third transfer material, the peel layer 602adhering the first metal layer 601 as a carrier layer to the secondmetal layer 603 as a wiring layer, a third metal layer 605 and thefourth metal layer 602 is weak in adhesive strength itself but excellentin etch resistance property. Thus, even if the entire five-layeredlaminate shown in FIG. 6D is subjected to an etching process, only thesecond metal layer 603 can be removed effectively and the transfermaterial can be formed without peeling off the interlayer portion of thelaminate. The adhesive strength between the first metal layer 601 andthe second metal layer 603 via the peel layer 602 was 40 N/m (gf/cm),exhibiting an excellent peeling property.

With such a third transfer, a three-layered wiring pattern including thesecond metal layer 603, the third metal layer 605 and fourth metal layer606 was transferred to the base material sheet (a material for thesubstrate). As a result, an adhesive plane (peel layer 602) between thefirst metal layer 601 and the second metal layer 603 was peeled offeasily and the three-layered wiring pattern was transferred to the basematerial.

In this Example, similar to Example 1, the carrier layer was formed ofcopper foil having a thickness of 35 μm, and even if the transfermaterial was deformed at the time of transfer, the carrier layer wasresistant to the deformation stress. On the other hand, in the transfermaterial in this example, the concave portion of the first metal layerthat is a carrier layer is secured to be as deep as 10 μm. Therefore,when the transfer material is pressed onto the base material sheet, thebase material extruded from the portion into which the wiring pattern isembedded is likely to flow into the concave portion, thus suppressingthe deformation stress that distorts the pattern in the verticaldirection.

Therefore, similar to Example 2, the distortion of the pattern in thisExample was only the amount generated by the curing and shrinking of thebase material (0.07%). This shows the effect of forming the concave andconvex portion in accordance with the wiring pattern also in the firstmetal layer that is a carrier layer. Furthermore, when the wiringresistance after transfer was measured, as compared with Example 1,because the thickness of the wiring pattern was increased by the thirdmetal layer, a cross sectional area for the wiring can be increased andreduce the resistance value by about 20 to 30%.

Furthermore, in this Example, since the outermost layer that is incontact with the base material in the wiring layer is formed of a silverplating layer, it was possible to stabilize the connecting propertybetween the wiring pattern and the conductive via paste mentioned belowin Example 5.

Furthermore, when the wiring pattern is formed on the substrate by usingthe transfer material of this Example, similar to the above-mentionedExamples, the concave shaped wiring pattern can contribute to thepositioning in a flip chip mounting. Furthermore, it is needless to saythat the carrier copper foil (first metal layer) on which the convexportion corresponding to the wiring pattern can be reused aftertransfer.

Example 5

A composite wiring substrate was produced by using the third transfermaterial formed in Example 4 as shown in FIG. 7A to 7C. In FIG. 7A to7C, a metal layer 701 corresponds to the fourth metal layer 606 of thethird transfer material according to Example 4, a metal layer 702corresponds to the third metal layer 605 of the third transfer material,a metal layer 703 corresponds to the second metal layer 603 of the thirdtransfer material, a metal layer 704 corresponds to the peel layer 602of the third transfer material, and a metal layer 705 corresponds to thefirst metal layer 601 of the third transfer material, respectively.

First, a substrate to which the wiring pattern is to be transferred wasprepared. This substrate was produced by preparing the base materialsheet 706 formed of composite materials shown below, providing the basematerial sheet with via holes, and filling the via holes with aconductive paste 707. Hereinafter, the component compositions of thebase material sheet 706 are described.

(Component Composition of the Base Material Sheet 706)

-   -   Al₂O₃ (AS-40 manufactured by Showa Denko K. K., average particle        diameter of 12 μm) 90 weight %    -   liquid epoxy resin (EF-450 manufactured by Nippon Rec Co. Ltd.)        9.5 weight %    -   carbon black (manufactured by Toyo Carbon) 0.2 weight %    -   coupling agent (46B, titanate based coupling agent manufactured        by Ajinomoto Co., Inc.) 0.3 weight %.

Each of the above-mentioned components was weighed so as to have theabove-mentioned composition weight ratio. A solvent of methyl ethylketone was added into the mixture of the above-mentioned components sothat the viscosity of the slurry mixture was about 20 Pa·s, and thenrotated and mixed by the use of alumina balls in a pot at the rotationrate of 500 rpm for 48 hours so as to form into a slurry.

Next, as a mold release film, a PET film having a thickness of 75 μm wasprepared. On the PET film, the slurry was formed into a film sheet at agap of about 0.7 mm by a doctor blade method. The film sheet was allowedto stand for 1 hour at 100° C. so as to volatilize the methyl ethylketone solvent and to remove the PET film, thus to form into a basematerial sheet 706 having a thickness of 350 μm. Since the solvent wasremoved at 100° C., the epoxy resin was kept to be uncured and the basematerial sheet 706 had a flexibility.

This base material sheet 706 was cut in a predetermined size by the useof its flexibility, and provided with through holes (via holes) having adiameter of 0.15 mm at equal intervals with a pitch of 0.2 to 2 mm.Then, the through holes were filled with a conductive paste for fillingvia holes 707 by a screen printing method. Thus, the substrate wasproduced. The conductive paste 707 to be used was obtained by mixing andkneading the following materials at the below mentioned compositions bythe use of a triple roller.

[Component Composition of the Conductive Paste 707]

-   -   spherical copper particles (Mitsui Mining & Smelting Co., Ltd.,        particle diameter of 2 μm) 85 weight %    -   bisphenol A epoxy resin (Epicoat 828 manufactured by Yuka Shell        Epoxy) 3 weight %    -   glycidyl ester based epoxy resin (YD-171 manufactured by Toto        Kasei) 9 weight %    -   amine adduct hardening agent (MY-24 manufactured by Ajinomoto        Co., Inc.) 3 weight %

Next, as shown in FIG. 7A, the third transfer material was placed sothat the side of the fourth metal layer 701 of the third transfermaterial was in contact with both surfaces of the base material sheet706, and heated and pressed by a thermal press treatment at a pressureof 9.8×10⁵ Pa (10 kgf/cm²) at a pressing temperature of 120° C. for 5minutes. With this heating and pressing treatment, an epoxy resin in thebase material sheet 706 and the conductive paste 707 was fused andsoftened. Thus, the wiring pattern including the second, third, andfourth metal layers 703, 702 and 701 was allowed to be embedded in thebase material sheet 706.

Then, the epoxy resin was cured by raising the heating temperature andtreated at 175° C. for 60 minutes. This led to strong connection betweenthe base material sheet 706 and the second, third, and fourth metallayers 703, 702 and 701. Furthermore, the conductive paste 707 and thefourth metal layer 701 were electrically connected (inner viaconnection) and strongly adhered to each other.

From the laminate shown in FIG. 7B, the first metal layer 705 (carrierlayer) and the peel layer 704 were peeled off together. Thus, the wiringsubstrate as shown in FIG. 7C including the second, third and fourthmetal layers 703, 702 and 701 transferred to both surfaces was obtained.This wiring substrate is referred to as a wiring substrate 7A. Thiswiring substrate 7A is provided with the concave portion correspondingto the depth of the concave portion formed by etching process on thesurface layer portion of the first metal layer 705. At the bottom of theconcave portion, the second, third, and fourth metal layers 703, 702 and701 were formed.

Furthermore, besides the wiring substrate 7A produced in this Example, awiring substrate (referred to as a wiring substrate 7B) also is producedby transferring the wiring pattern by using the first transfer materialdescribed in Example 1. In order to evaluate the reliability of the thuswiring substrates 7A and 7B, a solder reflow test and a temperaturecycling test were performed. The following are the methods of each test.

[Solder Reflow Test]

The solder reflow test was performed with a belt type reflow tester(manufactured by Matsushita Electric Industrial Co., Ltd.) in which a 10second cycle was repeated 10 times at a maximum temperature of 260° C.

[Temperature Cycling Test]

The temperature cycle test was performed by allowing the wiringsubstrate to stand at 125° C. for 30 minutes and then at −60° C. for 30minutes per cycle, and repeating this cycle for a total of 200 cycles.

In either the solder reflow test or the temperature cycle test, nocracks were generated in the wiring substrates 7A and 7B, andabnormality was not recognized, even if a supersonic flaw detector wasused. A resistance value of the inner via connection by the conductiveresin paste 707 was not substantially changed between measurements madebefore and after the tests.

The initial performance was hardly changed before and after the tests,however, the change rate was 5% or less in the wiring substrate 7A,while the change rate was 10% or less in the wiring substrate 7B. Bothvia connections of the wiring substrates had a sufficient stability,however, in the wiring substrate 7A in which Ag plating layer is presentin the connecting portion between the wiring layer and the conductiveresin paste, more stable via connection could be realized.

Example 6

A ceramic wiring substrate as shown in FIG. 8 was produced by using thetransfer material produced in Example 1.

First, a substrate to which the wiring pattern is to be transferred wasprepared. This substrate was produced by preparing a low temperaturesintering ceramic green sheet 805 including a low temperature sinteringceramic material and an organic binder, providing this green sheet withvia holes, and filling the via holes with conductive paste 806.Hereinafter, the component compositions of the green sheet 805 aredescribed.

(Component Composition of the Green Sheet 805)

-   -   mixture of ceramic powder Al₂O₃ and borosilicate glass (MLS-1000        manufactured by Nippon Electric Glass Co., Ltd.) 88 weight %    -   methacrylic acid based acrylic binder (Olicox, manufactured by        Kyoeisya Kagaku Co., Ltd.) 10 weight %    -   BBP (manufactured by Kanto Chemical Co., Inc.) 2 weight %

Each of the above-mentioned components is weighed so as to have theabove-mentioned composition weight ratio. A solvent of toluene was addedinto the mixture of the above-mentioned components so that the viscosityof the slurry mixture was about 20 Pa·s, and then rotated and mixed bythe use of alumina balls in a pot at the rotation rate of the 500 rpmfor 48 hours so as to form into a slurry.

Next, as a mold release film, a polyphenylene sulfide (PPS) film havinga thickness of 75 μm was prepared. On the PPS film, the slurry wasformed into a film sheet at a gap of about 0.4 mm by a doctor blademethod. The toluene solvent in the sheet was allowed to be volatilizedso as to remove the PES film, thus to form a green sheet 805 having athickness of 220 μm. Since in this green sheet 805, a plasticizer BBPwas added into the methacrylic acid based acrylic binder, flexibilityand excellent thermal decomposition property were exhibited.

This green sheet 805 was cut in a predetermined size by making use ofits flexibility, and provided with through holes (via holes) having adiameter of 0.15 mm at equal intervals with a pitch of 0.2 mm to 2 mm bythe use of a punching machine. Then, the through holes were filled witha conductive paste for filling via holes 806 by a screen printingmethod. Thus, the substrate was produced. The conductive paste 806 to beused was obtained by mixing and kneading the following materials at thefollowing compositions by the use of a triple roller.

[Component Composition of the Conductive Paste 806]

-   -   spherical silver particles (Mitsui Mining & Smelting Co., Ltd.,        particle diameter of 3 μm) 75 weight %    -   acrylic resin (manufactured by Kyoeisya Kagaku Co., Ltd.,        polymerization degree 100 cps) 5 weight %    -   borosilicate glass (manufactured by Nippon Electric Glass Co.,        Ltd) 3 weight %    -   terpineol (manufactured by Kanto Chemical Co., Inc.) 12 weight %    -   BBP (manufactured by Kanto Chemical Co., Inc.) 5 weight %

Next, the first transfer material produced in Example 1 was placed sothat the side of the second metal layer (wiring layer) was in contactwith both surfaces of the substrate, heated and pressed by a thermalpress treatment at a pressing temperature of 70° C. and at a pressure ofabout 5.88×10⁶ Pa (60 kgf/cm²) for 5 minutes. With this heating andpressing treatment, an acrylic resin in the substrate was fused andsoftened. Thus, the second metal layer (wiring layer), a peel layer, anda part (concave portion) of the first metal layer (carrier) of the firsttransfer material were embedded into the substrate.

After the laminate was cooled, the first metal layer (carrier) and apeel layer were peeled off from the laminate, and thereby only thesecond metal layer remained. As shown in FIG. 8, a wiring substrate 800having a wiring layer 801 formed of a second metal layer is formed onboth surfaces of the substrate was obtained.

Then, an alumina green sheet that is not sintered at the firingtemperature was laminated on both surfaces of the wiring substrate andfixed, by carrying out the binder removing process and firing in anatmosphere of nitrogen. First, in order to remove the organic binder inthe green sheet 805, the laminate was heated by the use of an electricfurnace in nitrogen up to 700° C. while raising temperatures at the rateof 25° C./hour, and treated at 700° C. for 2 hours. Then, the wiringsubstrate in which the binder was removed was burned by treating innitrogen at 900° C. for 20 minutes. The firing condition was set to be atemperature rising time of 20 minutes, temperature falling time of 20minutes and in/out total time of 60 minutes. After firing, the aluminagreen sheet was easily removed. Thus, a low temperature sinteringceramic wiring substrate 800 was produced.

On both surfaces of the wiring substrate 800, the concave portioncorresponding to the depth of the convex and concave of the first metallayer of the first transfer material was formed, and the wiringsubstrate 801 including the second metal layer was formed at the bottomof the concave portion. Furthermore, the surface wiring layers 801 onthe both surfaces were electrically connected to each other with aconductive metal sintering via that is formed by sintering theconductive paste 806 in the thickness direction. In the configuration ofthis Example, as shown in FIG. 8, a gold plating layer 802 was formed onthe second metal layer 801 of the wiring substrate 805.

Next, a configuration on which a bare semiconductor chip 905 wasflip-chip mounted on the surface of the low temperature sinteringceramic substrate 800 is explained. FIG. 9 is a cross sectional viewshowing one example of the schematic configuration in which a baresemiconductor chip 905 was flip-chip mounted on the surface of the lowtemperature sintering ceramic substrate 800.

First, a projecting bump 903 produced by a gold wire bonding was formedon an aluminum pad 904 on the surface of the bare semiconductor chip905, and thermosetting conductive adhesive agent (not shown) wastransferred on the bump 903. By adhering the projecting bump 903 to thegold plating layer 802 via a conductive adhesive agent while positioningthe projecting bump 903 with respect to the concave portion (wiringpattern portion) of the ceramic wiring substrate 800, the semiconductordevice 905 was mounted. Consequently, as mentioned above, in the concaveportion formed by transferring the second metal layer (wiring layer 801)by using the first transfer material, the bump 903 and the wiring layer(second metal layer 801 and gold plating layer 802) were connected.

In order to evaluate the reliability of the flip-chip mounted substrate,a solder reflow test and a temperature cycling test were carried out.Each test was carried out under the same conditions as in Example 4. Asa result, a resistance value of the bump connection in the ceramicwiring substrate 800 on which the semiconductor device 905 was flip-chipmounted was not substantially changed between measurements made beforeand after the tests and exhibited the stability.

When the transfer material shown in FIG. 2 having the second metal layerformed of Ag plating layer and the third metal layer formed of Agpattern plating layer was transferred, it was possible to transfer theAg plating wiring pattern to the ceramic green sheet 805. In this case,in the production process, since binder removing process and firingtreatment can be carried out in the air, it is advantageous from theviewpoint of cost. Furthermore, oxidation resistance property isremarkably improved.

Example 7

A multi-layered wiring substrate was produced by using a transfermaterial and a substrate formed of a composite material produced by thesame method as in Example 5. FIG. 10 is a cross-sectional view showingone example of a schematic configuration of the multi-layered wiringsubstrate.

As shown in FIG. 10A to 10J, reference numerals 1001 a, 1001 b and 1001c denote substrate sheets; 1002 a, 10002 b and 1002 c denote first metallayers that are carriers; 1003 a, 1003 b and 1003 c denote conductivepastes; 1004 a, 10004 b and 1004 c denote second metal layers serving asa wiring pattern; 1005 a, 1005 b and 1005 c denote peel layers; A, B, Cand D denote transfer materials, and E denotes a multi-layeredsubstrate, respectively.

Furthermore, in FIGS. 10A to 10I, FIGS. 10A, 10D and 10G show the stepsfor producing a single layered wiring pattern by using the transfermaterial A and the substrate 1001 a; similarly, FIGS. 10B, 10E and 10Hshow the steps for producing a single layered wiring pattern by usingthe transfer material B and the substrate 1001 b; and FIGS. 10C, 10F and10I show the steps for producing a single layered wiring pattern byusing the transfer materials C and D and the substrate 1001 c;respectively. Furthermore, FIG. 10J shows a multi-layered wiringsubstrate E produced by laminating the above-mentioned three singlelayered substrates. Unless otherwise noted, each single wiring substrateis produced by the same method as in Example 5.

First, the transfer materials A, B, C, and D shown in FIGS. 10A, 10B,and 10C were produced. First, electrolytic copper foils having athickness of 35 μm were produced as the first metal layers 1002 a, 1002b, 1002 c, and 1002 d by the same method for producing foils as inExample 1.

Next, the peel layers 1005 a, 1005 b, 1005 c and 1005 d made of a Ni—Palloy plating layer were formed thinly on the roughened surface of thefirst metal layers 1002 a, 1002 b, 1002 c, and 1002 d to the thicknessof 100 nm or less. Electrolytic copper foils having a thickness of 9 μmas the second metal layers for forming wiring patterns 1004 a, 1004 b,1004 c, and 1004 d were laminated thereon by the same electrolyticplating as in Example 1 so as to form a three-layered laminate. Herein,as the peel layer, a chrome plating layer can be used.

Next, an etching process using a base copper chloride aqueous solutioncapable of removing only copper was carried out from the side of thesecond metal layers for forming wiring patterns 1004 b and 1004 c so asto form the second metal layers 1004 b and 1004 c into desired wiringpatterns. Thus, transfer materials B, C shown in FIGS. 10B and 10C wereobtained. Similarly, an etching process with respect to copper and theNi—P alloy plating layer was carried out by a chemical etching processfrom the side of the second metal layers for forming wiring patterns1004 a and 1004 d so as to form the second metal layers 1004 a and 1004d into desired wiring patterns. At the same time, a convex and concaveportion corresponding to the wiring pattern was formed on the surfaceportion of the first metal layer 1002 a and 1002 d. Moreover, the convexportion corresponds to a region of the wiring patterns, and the concaveportion corresponds to a region excluding the wiring patterns. Thus,transfer materials A, D shown in FIGS. 10A and 10C were obtained.

Next, as shown in FIGS. 10A, 10B, and 10C, the second metal layers 1004a, 1004 b and 1004 c of the transfer materials A, B, C, and D wereplaced so that the side of the second metal layers 1004 a, 1004 b and1004 c were in contact with the surfaces of the substrate sheets 1001 a,1001 b and 1001 c. In FIG. 10C, the transfer materials C and D wereplaced, respectively on both surfaces of the substrate sheet 1001 c.

Then, as shown in FIGS. 10D, 10E, and 10F, the laminates of the transfermaterials A, B, C and D and the substrates 1001 a, 1001 b and 1001 cwere heated and pressed at a temperature of 100° C., and at a pressureof about 9.8×10⁵ Pa (10 kgf/cm²) for 5 minutes and epoxy resin in thesubstrate sheets 1001 a, 1001 b, 1001 c was fused and softened. Thus,the second, third, and fourth metal layers 1004 a, 1004 b, 1004 c, and1004 d were embedded in the substrate sheets 1001 a, 1001 b, and 1001 c,respectively.

Next, by peeling the first metal layers 1002 a, 1002 b, 1002 c and 1002d from the laminate together with the peel layers 1005 a, 1005 b, 1005c, and 1005 d, only the second metal layers 1004 a, 1004 b, 1004 c and1004 d are remained on the substrate sheets 1001 a, 1001 b and 1001 c.Thus, three kinds of single-layered wiring substrates, i.e., asingle-layered wiring substrate having a flat surface (FIG. 10H), asingle-layered wiring substrate having a concave portion on the wiringlayer portion (FIG. 10G), and a single-layered wiring substrate having aflat surface on one surface and the concave portion on another surface(FIG. 10I), were obtained.

Finally, as shown in FIG. 10J, the three kinds of single layered wiringsubstrates were laminated, and then heated and pressed at a temperatureof 175° C., and at a pressure of about 7.84×10⁶ Pa (80 kgf/cm²) for onehour so as to allow the laminate to be thermally cured and shrunk. Thus,a multi-layered substrate E was obtained. With this process, epoxy resinin the substrate sheets 1001 a, 1001 b, and 1001 c and the conductivepaste 1003 a, 1003 b, and 1003 c were cured, so that the mechanicalstrength of the multi-layered wiring substrate E was maintained.Furthermore, the second metal layers 1004 a; 1004 b, 1004 c and 1004 dwere electrically connected to each other with a conductive resin viapaste 1003 a, 1003 b, and 1003 c. Since the multi-layered substrate Ewas allowed to be thermally cured and shrunk in one time after thesingle layered wiring substrates were laminated, there was no viadeviation in a via-on-via structure.

The thus obtained multi-layered substrate E can form a fine wiringpattern with a line width of about 50 μm. Furthermore, since it had anIVH structure, it was useful as an extremely small and high densitymounted wiring substrate. In particular, since the wiring pattern wastransferred and formed by the use of the transfer material according tothe present invention, no dislocation occurs on the surface layer planein which the fine wiring patterns are concentrated. Thus, the yield rateis expected to be improved.

Furthermore, the wiring layer on the surface layer on which chips, etc.are mounted has a concave portion, and it was possible to carry out theflip chip mounting easily. Moreover, the multi-layered substrate of thepresent invention is not limited to the above-mentioned structure. Forexample, a multi-layered wiring substrate having a single layered wiringsubstrate having a wiring layer provided with a concave portion asmentioned above can be employed. The multi-layered substrate in thiscase also shows a low resistant and high reliable via connection.

Furthermore, when the second metal layer is made of copper foil, a goldplating layer can be formed on the upper layer portion in order toprevent oxidation. In this case, if the surface of the gold platinglayer also has a concave portion with respect to the substrate surface,it is possible to reduce the creeping distance even in a fine wiringpattern, and is advantageous from the viewpoint of preventing migration.

In this Example, the composite substrate was used. However, the basematerial is not necessarily limited thereto and a ceramic green sheetcan be used. In this case, a multi-layered substrate can be attained bythe same process except only the sintering process in the productionprocess explained in this Example.

Furthermore, in this Example, the first transfer material including awiring pattern made of the single layered metal layer was used. However,by using the second or third transfer material, a multi-layered wiringsubstrate having a plurality of metal layers can be produced.

Example 8

A multi-layered wiring substrate including a laminate made of a ceramicsubstrate and a substrate including at least a thermosetting resin wasproduced by using the first transfer material explained in Example 1.

First, a base material sheet, which is a material for a ceramic wiringsubstrate 1608 (see FIG. 16B) and to which a wiring pattern istransferred, was prepared. This base material sheet was produced bypreparing a low temperature sintering ceramic green sheet including alow temperature sintering ceramic material and an organic binder,providing this green sheet with via holes, and filling the via holeswith conductive paste 1609. Hereinafter, the component compositions ofthe green sheet are described.

[Component Composition of the Green Sheet]

-   -   mixture of ceramic powder Al₂O₃ and borosilicate glass (MLS-1000        manufactured by Nippon Electric Glass Co., Ltd) 88 weight %    -   methacrylic acid based acrylic binder (Olicox, manufactured by        Kyoeisya Kagaku Co., Ltd) 10 weight %    -   BBP (manufactured by Kanto Chemical Co., Inc.) 2 weight %

Each of the above-mentioned components was weighed so as to have theabove-mentioned composition weight ratio. A solvent of toluene was addedinto the mixture of the above-mentioned components so that the viscosityof the mixture slurry was about 20 Pa·s, and then rotated and mixed bythe use of alumina balls in a pot at the rotation rate of the 500 rpmfor 48 hours so as to form a slurry.

Next, as a mold release film, a polyphenylene sulfide (PPS) film havinga thickness of 75 μm was prepared. On the PPS film, the slurry wasformed into a film sheet at a gap of about 0.4 mm by a doctor blademethod. The toluene solvent in the sheet was allowed to be volatilizedso as to remove the PPS film, thus to form into a green sheet having athickness of 220 μm. Since in this green sheet, a plasticizer BBP wasadded into the methacrylic acid based acrylic binder, flexibility andexcellent thermal decomposition property were exhibited.

This green sheet was cut in a predetermined size by making use of itsflexibility, and provided with through holes (via holes) having adiameter of 0.15 mm at equally intervals with a pitch of 0.2 mm to 2 mmby the use of a punching machine. Then, the through holes were filledwith a conductive paste for filling via holes 1609 by a screen printingmethod. Thus, the base material sheet was produced. The conductive paste1609 to be used was obtained by mixing and kneading the followingmaterials at the following compositions by the use of a triple roller.

[Component Composition of the Conductive Paste 1609]

-   -   spherical silver particles (manufactured by Mitsui Mining &        Smelting Co., Ltd., particle diameter of 3 μm) 75 weight %    -   acrylic resin (manufactured by Kyoeisya Kagaku Co., Ltd,        polymerization degree 100 cps) 5 weight %    -   borosilicate glass (Nippon Electric Glass Co., Ltd) 15 weight %    -   BBP (manufactured by Kanto Chemical Co., Inc.) 5 weight %

Next, the first transfer material described in Example 1 was placed sothat the side of the second metal layer was in contact with bothsurfaces of the substrate, heated and pressed by a thermal presstreatment at a pressing temperature of 70° C. and at a pressure of about5.88×10⁶ Pa (60 kgf/cm²) for 5 minutes. With this heating and pressingtreatment, an acrylic resin in the substrate was fused and softened.Thus, the wiring layer (second metal layer), a peel layer, and a surfaceportion (concave portion) of the carrier (first metal layer) of thefirst transfer material were embedded into the substrate.

After the laminate is cooled, the carrier of the first transfer materialwas peeled off from the laminate together with a peel layer, therebyonly the second metal layer was remained on the laminate. As shown inFIG. 16B, a wiring substrate 1608 having a wiring layer 1610 formed of asecond metal layer is formed on both surfaces of the substrate wasobtained.

Then, an alumina green sheet that is not sintered at the firingtemperature was laminated on both surfaces of the ceramic substrate1608, and fixed, by carrying out the binder removing process and firingin an atmosphere of nitrogen. First, in order to remove the organicbinder in the ceramic wiring substrate 1608, the laminate was heated bythe use of an electric furnace in nitrogen up to 700° C. while raisingtemperatures at the rate of 25° C./hour, and treated at 700° C. for 2hours. Then, the ceramic wiring substrate 1608 in which the binder wasremoved was burned by treating in nitrogen at 900° C. for 20 minutes.The firing condition was set to be a temperature rising time of 20minutes, temperature falling time of 20 minutes and in/out total time of60 minutes. After firing, the alumina green sheet was removed easily.

Furthermore, as shown in FIG. 16B, wiring substrates 1605, 1606, and1607 made of composite materials were laminated as shown in FIGS. 16A to16C, with the ceramic wiring substrate 1608 that has been produced asmentioned above being sandwiched therebetween as shown in FIG. 16B.Thus, a laminate in which all layers were interlayer connected wasobtained.

Herein, the method for producing the composite wiring substrate 1605etc. is described. As shown in the uppermost part of the FIGS. 16A and16B, by using the first transfer material 1601 (the same as inExample 1) according to the present invention, the wiring pattern formedon the first transfer material is transferred to an uncured compositesheet (having the same composition as in Example 5, so that asingle-layered wiring substrate 1605 having a wiring pattern 1604 isformed. The composite sheet 1602 is provided with thorough holes, andthe through holes are filled with a conductive paste 1603. By the samemethod, the single-layered substrates 1606 and 1607 using the compositesheet 1602 are produced.

Thereafter, the composite single-layered wiring substrates 1605 to 1607were laminated on both surfaces of the ceramic wiring substrate 1607,and subjected to the thermal press treatment at a pressing temperatureof 200° C. and a pressure of about 2.94×10⁶ Pa (30 kgf/cm²) for 60minutes. With this heating and pressing treatment, an acrylic resin inthe composite sheet 1602 in the single-layered wiring substrates 1605 to1607 was fused and softened. Thus, the entire wiring substrate includingthe ceramic layer 1608 was cured and integrated into one piece as shownin FIG. 16C.

By the same method as in this Example, a multi-layered wiring substrateincluding a composite wiring substrate and the ceramic wiring substratewas produced as shown in FIG. 11 or FIG. 12. The configuration is thesame as that of the multi-layered wiring substrate shown in FIG. 11 orFIG. 12.

When the multi-layered wiring substrate shown in FIGS. 11 and 12produced by a method of this Example was observed by the use of anX-ray, no damaged portions such as cracks were generated in the ceramiclayer.

In addition, when the via connection resistance was evaluated, it wasshown that the multi-layered substrate had a low resistant viaconnection.

As shown in FIG. 11, when the ceramic wiring substrate 1608 was notprovided with the inner via holes and Ba—Ti—O ceramic was used for acapacitance layer, the high capacitance of 10 to 50 nF/cm² was realizedeasily.

Furthermore, an inner electrode layer may be formed on the resinsubstrate layer 1602 or may be formed in the ceramic layer 1608.

In addition, in this Example, the first transfer material was used forproducing the wiring layer of each single-layered wiring substrate.However, when the second or third transfer material may be used, it isalso possible to produce multi-layered wiring substrate having a wiringlayer including a plurality of metal layers.

Example 9

Another ceramic wiring substrate was produced. The ceramic wiringsubstrate has substantially the same configuration as in Example 8except that a ceramic wiring substrate that forms a ceramic layer isformed of such a material as Al₂O₃ sintered only at high temperature.FIGS. 17A to 17C show the production process of the multi-layeredsubstrate of this Example.

The multi-layered wiring substrate of this Example is characterized byincluding a substrate having a high strength and a high thermalconductivity, which cannot be realized by a low temperature sinteringceramic, and a low resistance wiring of a copper foil, etc.

First, an alumina green sheet was prepared as a material for a ceramicwiring substrate. This green sheet was provided with through holes andburned before being filled with a conductive paste mentioned below. Inthe firing process, since positional data of the thorough holes wereused also in the below mentioned resin substrate (composite wiringsubstrate), a green sheet formed of SiC that is not sintered at thefiring temperature was laminated on both surfaces of the alumina greensheet. Then, the laminate was fixed by carrying out the binder removingprocess and firing in the air. First, in order to remove the organicbinder in the alumina green sheet, the laminate was heated by the use ofan electric furnace in nitrogen up to 700° C. while raising temperaturesat 25° C./hour, and treated at 1600° C. for 2 hours. After firing, itwas possible to remove a SiC layer easily and to obtain an Al₂O₃substrate 1708 that has been sintered in a non-shrinkage state in theplane direction. In this Example, a non-shrinkage process using aconstrained layer was carried out, however, a usual sintering andshrinkage process may be employed, in which equal shrinkage in threedimensions by correcting the shrinkage amount.

The via holes having a diameter of 0.15 mm that had been formedbeforehand on the Al₂O₃ substrate 1708 were filled with a thermosettingconductive paste for filling via holes 1704 by a screen printing method.The conductive paste 1704 had the same component composition asexplained in Example 8.

Furthermore, as shown in FIG. 17B, wiring substrates 1705 to 1707 madeof the composite sheet 1702 were laminated with the Al₂O₃ substrate 1708sandwiched therebetween. Thus, as shown in FIG. 17C, a multi-layeredwiring substrate 1709 in which all layers were interlayer connected wasobtained.

Herein, the method for producing the wiring substrates 1705 to 1707using the composite sheet 1702 is described. As shown in FIG. 17A, thefirst transfer material 1701 (the same as in Example 8 according to thepresent invention is pressed onto the uncured composite sheet 1702 (thesame configuration as in Example 8.

The composite sheet 1702 was provided with through holes, and thethrough holes were filled with a conductive paste 1704 that is the samepaste filled in the Al₂O₃ substrate 1708. As positional data for formingthrough holes, the same data used in forming though holes on the Al₂O₃substrate 1708 were used.

Then, similar to Example 8, by peeling off the carrier of the firsttransfer material together with the peel layer, only the wiring layer ofthe first transfer material remains on the composite sheet 1702. Thus,as shown in the top part of the FIG. 17B, the composite wiring substrate1705 having a wiring layer 1703 was produced. By the same method,composite substrates 1706 and 1707 were produced.

Thereafter, the composite wiring substrates 1705 to 1707 were laminatedon both surfaces of the Al₂O₃ substrate 1708, and subjected to thethermal press treatment at a pressing temperature of 200° C., and at apressure of about 2.94×10⁶ Pa (30 kgf/cm²) for 60 minutes. With thisheating and pressing treatment, an acrylic resin in the composite sheets1705 to 1707 were fused and softened. Thus, the entire wiring substratesincluding the Al₂O₃ substrate 1708 were cured and integrated into onepiece as shown in FIG. 17C. Thus, a multi-layered wiring substrate 1709was produced. The multi-layered wiring substrate has the sameconfiguration as the multi-layered wiring substrate shown in FIG. 13.

When the multi-layered wiring substrate shown in FIG. 17C and FIG. 13were observed by the use of an X-ray, no damaged portions such as crackswere generated in the Al₂O₃ substrate. Since the Al₂O₃ substrate had astrong mechanical strength, even if the pressure was set to be about9.8×10⁶ Pa (100 kgf/cm²), no damaged portions such as cracks wereobserved. Thus, it was possible to obtain a multi-layered wiringsubstrate excellent in mechanical strength such as transverse strengthetc.

In addition, when the via connection resistance of the multi-layeredwiring substrate 1709 was evaluated, a copper wiring formed in acomposite layer served as the low resistance wiring formed in a Al₂O₃layer. A low resistance via connection and wiring resistance wereconfirmed. The thermal conductivity of the multi-layered substrate 1709was a high thermal conductivity of about 6 W/m·K, because a compositesheet having a high thermal conductivity was used for the resinsubstrate.

In this Example, the ceramic layer and the composite layer used the sameconductive resin paste so as to form an inner via. However, differentthermosetting conductive pastes may be used. Furthermore, the basematerial used for the ceramic layer is not limited to Al₂O₃, and AlNhaving a high thermal conductivity, a low temperature burned glassceramic, and the like, may be used.

Example 10

In the multi-layered wiring substrates in Example 8 or 9, the wiringsubstrate including a resin sheet on the surface portion and a ceramicsubstrate in the middle layer. In this Example, as shown in FIG. 14, aceramic layer 1801, a resin sheet 1803, and a ceramic layer 1802 werelaminated in this order. In other words, the ceramic wiring substratewas placed on the surface portion and the wiring substrate using a resinsheet was placed the inside layer.

In the multi-layered wiring substrate of this Example, a high dielectriclayer such as a Nd₂O₅.TiO₂.SiO₂ based glass ceramic etc. is used as aceramic layer 1801 and a low dielectric layer formed of Al₂O₃ layer andborosilicate glass was used for a ceramic layer 1802. Thus, two layerseach having the different dielectric constant were laminated via theresin sheet 1803 so as to form a dissimilar laminate.

The ceramic layer is not necessarily limited to such a combination.First, a dissimilar laminate including different kinds of dielectriclayers, for example, a magnetic material such as ferrite, etc. and aBa—Ti—O based dielectric material is also possible.

The multi-layered wiring substrate has the following advantages. First,when the different kinds of ceramic layers are laminated directly,problems, for example, a mutual diffusion, warp, or the like, occur.Therefore, it may be difficult to combine ceramic layers in accordancewith the kinds of ceramic layers. However, by interposing a resin sheetbetween ceramic layers, it was possible to laminate the different kindsof layers easily regardless of the kinds of ceramic layers. Secondary,since the resin sheet is interposed between the ceramic layers, at thetime of laminating layers, no damaged portions such as cracks aregenerated in the ceramic layer.

The multi-layered wiring substrate of this Example was produced as shownin FIG. 18.

First, a Nd₂O₅.TiO₂.SiO₂ based glass ceramic green sheet 1801 and agreen sheet 1802 formed of an Al₂O₃ layer and a borosilicate glass (thesame configuration as in Example 8) were prepared.

These green sheets were provided with through holes and the throughholes were filled with a conductive paste 1803 (the same as in Example8. Then, as shown in FIG. 18A, transfer materials 1804 and 1805 having awiring pattern were laminated while positioning from both surfaces. Thelaminate was heated and pressed at 80° C. as shown in FIG. 18B, andthereafter the carrier was peeled off. Thereby, as shown in FIG. 18C,the wiring patterns of the transfer materials 1804 and 1805 weretransferred and formed on the green sheet 1801. Similarly, wiringpatterns were transferred to the green sheet 1802.

In this Example, as a positioning means for forming laminate, a pinlamination is employed. Therefore, at predetermined positions on thegreen sheet 1801 and 1802, through holes having diameters of 3 mm φ to3.3 mm φ were provided. Since the green sheets 1801 and 1802 share thepositional data of the through holes with the resin substrate, they arerequired not to shrink in the firing process. Therefore, on bothsurfaces of the laminate, a green sheet formed of Al₂O₃ that is notsintered at the firing temperature was laminated, and the laminate wasfixed by carrying out the binder removing process and firing in the air.First, in order to remove the organic binder in the green sheets 1801and 1802, the laminate was heated in nitrogen by the use of an electricfurnace up to 700° C. while raising temperatures at 25° C./hour, andtreated at 900° C. for 2 hours. After firing, it was possible to removethe Al₂O₃ layer easily and to obtain a Nd₂O₅.TiO₂.SiO₂ based glassceramic substrate (1801) and an Al₂O₃ group substrate (1802), which havebeen sintered in a non-shrinkage state in the plane direction.

Next, as shown in FIG. 18D, a composite sheet 1807 filled with aconductive paste 1806 was placed between ceramic layers, that is,between the green sheets 1801 and 1802, and previously positionedthereof by the use of a pin. Thereafter, thermal press treatment wascarried out at a pressing temperature of 170° C. and a pressure of7.84×10⁶ Pa (80 kgf/cm²) for 30 minutes.

Herein, when the pin for positioning had a diameter of 3 mm φ, via holesthat was not filled with paste were partially shrunk. It was difficultto allow the pin to penetrate through some of the via holes. However, asto the via holes in which somewhat larger via holes (3.06 mm φ to 3.3 mmφ) were provided by punching by taking a shrinkage into account, it waspossible to allow the pin to pass through the via holes without anydifficulties. In this case, the punching diameter may set to be 3 mm φand the diameter of the pin may be made to be thinner than 3 mm φ.

Furthermore, with the heating and pressing treatment at the time ofpressing the laminate, the epoxy resin in the composite sheet 1807 wasfused and softened. Thus, a multi-layered wiring substrate in which thegreen sheets 1801 and 1802 that are ceramic layers were integrated wasobtained (FIG. 18E). The multi-layered wiring substrate has the sameconfiguration as the multi-layered wiring substrate shown in FIG. 14.

In the composite sheet 1807 in this Example, the wiring pattern is notformed. Occasionally, a wiring pattern may be transferred in an uncuredstate.

Furthermore, in this Example, the composite sheet formed of an inorganicfiller and an epoxy resin was used. However the composite sheet is notnecessarily limited thereto, and any composite sheets, for example, aresin sheet without containing inorganic fillers, a prepreg containingglass fabrics, a prepreg formed of an aramide resin and a glass wovenfabric, may be used.

In this Example, a sintering process that is not substantially shrunk inthe plane direction was employed, however, a sintering process of anequal shrinkage in three dimension may be employed.

When the multi-layered wiring substrate shown in FIG. 18E was observed,no damaged portions such as cracks were generated in the ceramic layer.

In addition, when the via connection resistance of this laminate wasevaluated, the low resistant via connection was confirmed. Furthermore,when the multi-layered wiring substrate was allowed to pass through areflow furnace (JEDEC level 1) at 230° C. after moisture adsorption withrespect to the multi-layered wiring substrate (85° C., 85 Rh, 168 hr),as compared with the case where the via connection resistance in whichonly resin substrates were laminated, the via connection resistance withextremely smaller resistance fluctuation was realized. This is an effectof the high adsorption resistance property of the ceramic layer.

On the other hand, as shown in for example FIG. 15, a configuration inwhich the resin base layer 1807 was laminated on both surfaces of themulti-layered substrate shown in FIG. 14 (or FIG. 18E) was produced as atrial product (configurations of the ceramic layer, and the resin basedlayer were the same as in this Example). When the drop test with respectto the trial product was carried out, as compared with the configurationusing only the ceramic wiring substrate, it was confirmed that extremelylittle damage such as cracks was generated.

The base material to be used in the resin layer 1807 that is anoutermost layer is not necessarily a composite sheet used in the middlelayer. It can be selected for in accordance with the applications ofuse, and for example, a glass epoxy resin, etc. can be used.

The above-mentioned results show that the substrate having both anadvantage of a ceramic and an advantage of a resin can be realized.

As mentioned above, the present invention can provide a transfermaterial capable of transferring a fine wiring pattern at a lowtemperature without distortion of pattern, reliably and easily. And byusing the transfer material, it is possible to realize a wiringsubstrate having a fine wiring pattern and advantageous in flip-chipmounting of the semiconductor device, etc.

Furthermore, since the transfer material has a wiring layer formed in aconvex shape, an IVH can be compressed easily. Thus, it is advantageousin stabilizing the via connection.

Furthermore, since the transfer material of the present inventiontransfers only the wiring pattern (second metal layer etc.), so that thematerials for forming the first metal layer that is a carrier can bereused, thus realizing a low cost. Furthermore, it is useful from theviewpoint of industrial applicability.

Furthermore, the wiring substrate of the present invention has aconfiguration in which a wiring pattern is not projected from thesubstrate. Thus, the multi-layered wiring substrate in which a ceramicwiring substrate and a resin base wiring substrate are laminated, whichhas been difficult to form due to the damage for the ceramic layer atthe lamination, easily can be produced.

Moreover, in each of the transfer materials of Examples 1 to 10, it isalso possible to form circuit components such as an inductor, acapacitor, a resistor, a semiconductor device, or the like, forelectrically connecting to the wiring pattern, and to transfer them tothe substrate together with the wiring pattern. It is preferable thatthe passive components such as inductor, capacitor, and resistor, etc.are formed on the substrate by a printing method, for example a screenprinting method.

Fifth Embodiment

In the above-mentioned embodiments, the transfer materials fortransferring the wiring pattern to the substrate (first to thirdtransfer materials) are explained. The following embodiments describeanother transfer materials according to the present invention, that is,a component and wiring pattern transfer and formation material fortransferring a wiring pattern and a circuit component to the substratesimultaneously.

FIGS. 19A and 19B are cross-sectional views showing a schematicconfiguration of a component and wiring pattern transfer and formationmaterial (hereinafter, fourth transfer material will be referred to)according to one embodiment of the present invention.

As shown in FIG. 19A, in a fourth transfer material 2001A, on a wiringpattern transfer and formation material having a two-layered structurein which a wiring metal foil 2102 that is a second metal layer is formedon a mold release carrier metal foil 2101 that is a first metal layer,circuit components (an inductor 2103, a capacitor 2104 and a resistor2105) are formed for electrically connecting to the wiring metal foil2102 by a printing method.

Furthermore, as shown in FIG. 19B, numeral 2001B denotes anotherembodiment of the fourth transfer material. The transfer material 2001Bhas substantially the same configuration as the transfer material 2001Ashown in FIG. 19A. However, in this embodiment, not only a passivecomponent such as the inductor 2103, the capacitor 2104, the resistor2105, etc., but also a positive component such as a semiconductor chip2106, etc. is flip-chip mounted on a connection portion 2107 so that thecomponents are adhered to the wiring metal foil 2102.

Each of the transfer materials shown in FIGS. 19A and 19B is pressedonto the substrate and only the mold release carrier 2101 is peeled off.Thus, components excluding the mold release carrier 2101, that is, themetal foil for wiring 2102, the inductor 2103, the capacitor 2104, andthe resistor 2105, etc., and a positive component such as thesemiconductor chip 2106, etc. can be transferred to the substrate.

Sixth Embodiment

Next, FIG. 20 shows a schematic configuration of a component and wiringpattern transfer and formation material (hereinafter, a fifth transfermaterial will be referred to) according to a sixth embodiment of thepresent invention.

As shown in FIG. 20, in a fifth transfer material 2002, on a wiringpattern transfer and formation material having a three-layered structurein which a mold release carrier metal foil 2201 that is a first metallayer, a peel layer 2202 formed on the first metal layer, and a wiringmetal foil 2203 that is a second metal layer formed on the peel layer2202, an inductor 2204, a capacitor 2205 and a resistor 2206 are formedfor electrically connecting the wiring metal foil 2203 by a printingmethod.

Seventh Embodiment

Next, FIG. 21 shows a schematic configuration of a component and wiringpattern transfer and formation material (hereinafter, a sixth transfermaterial will be referred to) according to a further embodiment of thepresent invention.

As shown in FIG. 21, in a sixth transfer material 2003, on a wiringpattern transfer and formation material having a three-layered structurein which a mold release carrier metal foil 2301 that is a first metallayer, a peel layer 2302, and a wiring metal foil 2303 that is a secondmetal layer, an inductor 2304, a capacitor 2305 and a resistor 2306 areformed for electrically connecting to the wiring metal foil 2303 by aprinting method.

The mold release carrier metal foil 2301 has a concave and convexportion on the surface portion thereof The convex portion corresponds toa wiring pattern. On the region of the convex portions, a peel layer2302 made of an organic layer or a metal plating layer and a metal foilfor wiring 2303 are formed. The mold release carrier metal foil 2301 isadhered to the metal foil for wiring 2303 via the peel layer 2302.

It is preferable in the fourth to sixth transfer materials that theadhesive strength between the first metal layer and the second metallayer via the peel layer is weak, for example, 50 N/m (gf/cm) or less.In the fourth transfer material, by plating or an evaporation method,two metal layers are not peeled off from each other in the processes ofetching, plating, washing in water, and the like. However, it is shownthat only the second metal layer can be peeled off easily in a peelingprocess. Furthermore, a passive component pattern formed by a printingmethod can be peeled off easily from the first metal layer that is acarrier.

On the other hand, in the fifth and sixth transfer materials, a thinorganic layer having an adhesive strength and a thickness of less than 1μm is used for the peel layer. As the material for the organic layer,for example, an urethane resin, an epoxy resin, a phenol resin, and thelike, which are thermosetting resins, can be used. However, the materialis not necessarily limited thereto, and other thermoplastic resin, etc.can be used. However, if the thickness is 1 μm or more, the peelingproperty of the peel layer is deteriorated, which may make the transferdifficult.

On the other hand, in order to lower the adhesive strengthintentionally, a plating layer may be interposed as the peel layer. Forexample, a nickel plating layer, a nickel-phosphorous alloy layer, analuminum plating layer, or the like, having a thickness of less than 1μm, can be used as the peel layer so as to provide the transfer materialwith a peeling property.

Thus, in the wiring portion including a second metal layer, at the timeof transfer, the second metal layer can be peeled off from the firstmetal layer easily, and the second metal layer and component pattern canbe transferred to the substrate easily. A suitable thickness of the peellayer formed of the metal layer is about 100 nm to 1 μm. Since theprocess cost is increased with the increase in thickness, the thicknessis desirably less than 1 μm.

Moreover, in the fifth and sixth transfer materials, the second metallayer and the passive component pattern formed by a printing method canbe peeled off easily from the first metal layer that is a carrier.

Furthermore, it is preferable in the fourth to sixth transfer materialsthat the first metal layer includes at least one metal selected from thegroup consisting of copper, aluminum, silver and nickel, andparticularly copper. Furthermore, it is preferable that the second metallayer, similar to the first metal layer, includes at least one metalselected from the group consisting of copper, aluminum, silver andnickel. It is preferable that the fourth transfer material includessilver, and the firth and sixth transfer materials include copper.Copper is used for the first metal layer because of its low cost.Namely, copper foils having various kinds of predetermined thickness arecommercially available. Copper is used for the second layer because ofits easiness in plating.

Furthermore, in the sixth transfer material, there is an effect ofcontrolling a process with one etching liquid if the first metal layerand the second metal layer are formed of the same metal. In particular,when the metal layers are formed of copper, it is advantageous in thatthe conditions for carrying out the etching process have beeninvestigated in detail. Moreover, one kind of metal may be used, and thecombination of two metals or more may be used.

Furthermore, it is preferable in, for example, an etching process etc.of the sixth transfer material that when the peel layer and the surfaceportion of the first metal layer are removed by etching process (seeFIG. 21), the first metal layer and the second metal layer include thesame metal component. Moreover, in a case where the plating layer isused for a peel layer, the configuration shown in FIG. 21 can beprocessed with a copper etching liquid, but the configuration shown inFIG. 20 cannot be processed with a copper etching liquid. Furthermore,in the case where the first metal layer and the second metal layerinclude the same metal components, the kinds of the metal are notparticularly limited. However, it is formed of a copper foil preferably,and particularly preferably an electrolytic copper foil because of itsexcellent conductivity. Moreover, one kind of metal may be used, and thecombination of two metals or more may be used.

In the fourth to sixth transfer materials, the thickness of the firstmetal layer is preferably 1 to 18 μm, and more preferably 3 to 12 μm.When the thickness is less than 3 μm, when the second metal layer istransferred to the substrate, an excellent electric conductivity may notbe exhibited. On the contrary, when the thickness is 18 μm or more, itmay be difficult to form a fine wiring pattern.

In the fourth and fifth transfer materials, the thickness of the firstmetal layer is preferably 4 to 10 μm, and more preferably 20 to 70 μm.The first metal layer serves as a carrier, and occasionally, as shown inFIG. 21, the surface portion thereof as well as the wiring pattern isetched so as to form a convex and concave portion. Therefore, the firstmetal layer is desired to be a metal layer having a sufficientthickness. Furthermore, since the fourth to fifth transfer materialshave a carrier layer that is a metal layer (first metal layer), theyexhibit sufficient mechanical strength or thermal resistance withrespect to the thermal distortion or stress distortion in the directionof the plane, which are generated at the time of transfer.

The material for forming passive components electrically connected tothe wiring pattern is a paste material. It is preferable that when thesubstrate to which the passive components are transferred is made of,for example, a thermosetting resin, a material for the passivecomponents also contains the thermosetting resin. When the inductor isformed, a magnetic metal powder or ferrite is used as the filler to bemixed in the thermosetting resin. When the capacitor is formed, a highdielectric ceramic powder, for example, barium titanate, Pb basedperovskite, or the like, is used similarly as the filler. When variouskinds of resistors are formed, carbon, etc. is used as the filler. Inthis case, by varying the content of carbon, the resistance value can beadjusted. When the resistor is formed in a thin film, Nichrome alloy,chromium silicon, tantalum nitride, ITO, or the like, is used.

On the other hand, with the fourth or fifth transfer material, a patterntransfer can be formed at low temperature of 100° C. or less, so that itis possible to form a component wiring pattern on the ceramic greensheet.

On the other hand, when the substrate to which the passive componentsare transferred is a ceramic, a material (paste) to be used for printingthe passive component is preferably a material in which only filler isremained through the binder removing process. Therefore, a vehicle inwhich a binder having an excellent thermal deformation property isdissolved, for example, paste vehicle in which a binder is dissolved interpineol, is used. Specifically, the paste material capable of screenprinting is formed by kneading various fillers corresponding to theproperty of the inductor, the capacitor, and the resistor, respectively,by the use of a triple roller.

When the inductor is formed, a material obtained by mixing a magneticmetal powder, or a ferrite that is sintered at low temperature as thefiller with a glass is used as the filler. When the capacitor is formed,barium titanate, glass, and Pb based perovskite, and the like, is usedas the filler similarly. When the resistor is formed, a materialobtained by mixing a ruthenium pyrochlore, ruthenium oxide, lanthanumborite, as a filler, with glass is used. These materials can be sinteredtogether with the substrate ceramic that is sintered at a lowtemperature. Furthermore, even in the case of the inner layer resistor,it is possible to adjust the resistant value relatively easily.

Eighth Embodiment

One example of a method for producing the fourth transfer material (seeFIGS. 19A and 19B) is described in this embodiment.

This production method includes the following steps (1) and (2);

-   -   (1) forming a two-layered structure in which a second metal        layer 2403 that is a wiring pattern is directly adhered to the        first metal layer 2401 that is a carrier (see FIGS. 22A to 22E);        and    -   (2) forming component patterns 2405, 2406, 2407 and 2408 by a        printing method with positioning so that they are electrically        connected to the second metal layer 2403 (see FIGS. 22E and        22E′).

In the steps shown in FIGS. 22A to 22E′, a pattern opposite to thewiring pattern is formed on the first metal layer 2401 by using a dryfilm resist 2404 and then, the wiring pattern formed of a metal foil(second meat layer 2403) is formed by a direct drawing method, forexample, pattern plating or a sputtering method, an evaporation method,and the like. Thus, it is possible to form a fine wiring pattern.

Furthermore, when it is produced by plating, a metal foil forming asecond metal layer 2402 may be the same as the metal foil (for example,a copper foil) forming the first metal layer 2401 or may be formed of asilver plating film that is a different metal. Furthermore, the metalfoil of the first metal layer can be reused. Therefore, low cost can berealized and the industrial applicability is excellent.

A suitable method for forming passive components for electricallyconnecting the wiring pattern is a printing method. As the printingmethod, any of an off set printing, a gravure printing, a screenprinting, etc, may be employed, however, the screen printing method ispreferred. In the pattern used for the resistor, the suitable thicknesssometimes is 1 μm or less. In such a case, a dielectric layer producedby a PVD method or a CVD method can be attached.

The line width of the wiring pattern is usually required to be as thinas about 25 μm. In the present invention, such a line width ispreferred.

Ninth Embodiment

FIGS. 23A to 23F show one example of a method for producing the fifthtransfer material (see FIG. 20).

This production method includes the following steps (1) to (3);

-   -   (1) forming a three-layered laminate in which a first metal        layer 2501, a peel layer 2502 made of an organic layer or a        metal plating layer and the second metal layer 2503 containing        the same metal component as that contained in the first metal        layer 2501 are laminated (see FIG. 23A);    -   (2) forming a wiring pattern for transfer 2503 a (see FIG. 23E)        by processing the second metal layer 2503 into a wiring pattern,        with an entire peel layer maintained, by a chemical etching        process (see FIGS. 23B to 23E); and    -   (3) forming component patterns (an inductor 2505, a capacitor        2506 and a resistor 2507) by a printing method with positioning        so that they are electrically connected to the layer 2503 (see        FIG. 23F);    -   In the process for forming the wiring pattern described in (2),        in the step shown in FIG. 23B, a dry film resist 2504 is adhered        to the second metal layer 2503. In the step shown in FIG. 23C,        the wiring pattern region is formed by exposing the pattern. In        the step shown in FIG. 23D, the dry film resist is removed from        a region (2504 b) excluding the wiring pattern 2504 a by        developing and etching. In the step shown in FIG. 23E, the        remained dry film resist is removed.

Specifically, the chemical etching process is carried out as follows.When the aqueous solution of basic cupric chloride including an ammoniumion is used as an etchant, when the peel layer 2502 is formed of, forexample, a nickel-phosphorous alloy layer, only the second metal layer2503 can be etched. Thereafter, by using, as an etching liquid, a mixedliquid including nitrate and hydrogen peroxide solution, only the peellayer 2502 can be removed. With this method, the wiring portiontransferred to the substrate does not become a concave portion. Thus,the surface of the substrate can be made flat.

Tenth Embodiment

Next, FIGS. 24A to 24F show one example of a method for producing thesixth transfer material (see FIG. 21).

The steps of FIGS. 24A to 24F are the same as in the method forproducing the fifth transfer material of the ninth embodiment except thefollowing steps.

In other words, in the method for producing the fifth transfer material,only the second metal layer and the peeling layer are processed into thepattern by a chemical etching process, however, in the method forproducing the sixth transfer material, the surface portion of the firstmetal layer 2601 also is processed into the wiring pattern by thechemical etching process as shown in FIGS. 24D and 24E. Namely, a convexand concave portion is formed on the surface portion of the first metallayer 2601. As shown in FIG. 24F, component patterns (an inductor 2605,a capacitor 2606, and a resistor 2607) are formed by printing withpositioning so that the components are electrically connected to thewiring pattern.

According to the method for producing the fourth to sixth transfermaterials, it is possible to form a fine wiring pattern because themetal layer of the wiring pattern is formed by a chemical etchingprocess such as photolithography, etc. Furthermore, in the case of themethod for producing the sixth transfer material, by making the metalfoil of the wiring pattern (second metal layer) to be the same as thatcontained in the metal foil of a carrier (first metal layer), it ispossible to make the surface portion of the carrier to have the sameconvex and concave portion as that of the wiring pattern in one etchingprocess.

As mentioned above, it is possible to reuse the component materialsexcept the second metal layer. Furthermore, in the sixth transfermaterial, since the first metal layer is processed in a wiring pattern,it is possible to reuse the first metal layer in a different patternformation as letterpress printing. Therefore, a low cost and excellentindustrial applicability can be realized.

Moreover, in the method for producing the fourth to sixth transfermaterials, the second metal layer is formed by electrolytic plating.Furthermore, a further metal layer (third metal layer) may be formed byelectrolytic plating on the second metal layer. When the third metallayer or second metal layer for forming wiring pattern is formed byelectrolytic plating, appropriate adhesive strength can be obtainedbetween the second metal layer and the third metal layer. Moreover, agap between the metal layers occurs, so that an excellent wiring patterncan be formed. Or, the pattern can be formed by masking the wiringpattern after the third metal layer is formed on the second metal layerby panel plating. In this case, an effect of preventing the surface ofthe transferred second metal layer from being oxidized and improving thewettability of the soldering can be obtained.

Moreover, it is preferable in the method for producing the wiringpattern for transfer that before the third metal layer is formed on thesecond metal layer, the surface of the second metal layer is roughened.The term “before the third metal layer is formed” means before a maskfor forming the wiring pattern is formed on the second metal layer, orbefore the third metal layer is formed along the wiring pattern on thesecond metal layer on which masking is performed in the wiring patternThus, the second metal layer is roughened, the adhesion between thesecond metal layer and the third metal layer is improved.

Furthermore, it is preferable in the method for producing the transfermaterial that the fourth metal layer that is different from the first tothird metal layers can be formed by electrolytic plating. It ispreferable that by selecting a component that is chemically stable withrespect to the etching liquid corroding the first to third metal layersas the material for the fourth metal layer, the second, third, andfourth metal layers can be processed into the wiring pattern along withthe surface layer portion of the first metal layer without reducing thethickness of the second, third, and fourth metal layers.

For the fourth metal layer, for example, Ag, Au, or the like, havingchemical stability and the low resistance property are desirable. Sincethese metals are not likely to be oxidized, the adhesion between theplating wiring layer plated with these metals and for example, a viahole that is preliminarily formed on the substrate, a bump of a barechip, or conductive adhesive can be further stabilized.

In the method for producing the fifth and sixth transfer materials, as amethod for forming passive components for electrically connecting thewiring pattern, a printing method is suitable same as in the fourthtransfer material. When the peel layer is formed of a plating layer suchas a nickel plating layer or a nickel-phosphorous alloy layer, as theprinting method, any of an off set printing, a gravure printing, screenprinting, etc may be employed, and the screen printing is preferred.

Furthermore, the materials used for printing of the component patternare preferred to be paste. As in the fourth transfer material, when thesubstrate on which the passive components are transferred is made of,for example, a thermosetting resin, a material for the passivecomponents also contains the thermosetting resin. When the inductor isformed, as the filler to be mixed with the thermosetting resin, amagnetic metal powder or ferrite can be used. When the capacitor isformed, as the filler similarly, high dielectric ceramic powder, forexample, barium titanate, Pb based perovskite, or the like, can be used.When the resistor is formed, as the filler, carbon is used. As to theresistance value, by varying the content of carbon, the resistance valuecan be controlled. When the resistor is formed in a form of a thin film.The material for a resistor and the production method are the same as inthe fourth transfer material.

Since in the fifth transfer material, like a fourth transfer material, apattern transfer can be formed at low temperature of 100° C. or less, sothat it is possible to form a component wiring pattern on the ceramicgreen sheet.

When the substrate on which the components are transferred is a ceramicsubstrate, a material (paste) to be used for printing the componentpattern is preferably a material in which only the filler remains aftera binder removing process. Therefore, a vehicle in which a binder havingan excellent thermal deformation property is dissolved, for example,paste vehicle in which a binder is dissolved in terpineol is used.Specifically, the paste material capable of screen printing is formed bykneading various fillers corresponding to the property of the inductor,capacitor, and resistor, respectively, by using a triple roller.

When the inductor is formed, a material obtained by mixing a glass andfiller is used. As the filler, a magnetic metal powder and a ferritethat is sintered at low temperature with are used. When the capacitor isformed, as the filler similarly, barium titanate, Pb based perovskite,or the like is used. When the resistor is formed, as the filler, amaterial obtained by mixing a ruthenium pyrochlore, ruthenium oxide,lanthanum borite with a glass is used. These materials can be sinteredtogether with the ceramic substrate that is sintered at a lowtemperature. Furthermore, even in the case of an inner layer resistor,it is possible to adjust the resistance value relatively easily.

These two kinds of fifth and sixth component and wiring patternformation and transfer materials can be used in different waysappropriately. For example, when the component wiring pattern formed inthe transfer material is transferred to the inside layer of the laminatesubstrate, in particular, when the via is formed directly on the via, itis preferable that the transfer material shown in FIG. 20 (fifthtransfer material) is preferably used, from the viewpoint of the viaconnection.

On the other hand, when transferred to the surface portion, inparticular, when the distance between terminals of the inductor,capacitor, semiconductor chip is small, the transfer material (sixthtransfer material) that is partially processed to the carrier layershown in FIG. 21 is preferred form the purpose of reducing the creepingdistance.

Eleventh Embodiment

Next, FIGS. 22G, 22G′, 23H, and 24H show one embodiment of the circuitcomponent produced by the use of the fourth to sixth transfer materials.

A circuit substrate using the fourth to sixth transfer materials can beproduced by at least two methods. The first method for producing thisembodiment includes the following steps:

A step in which the transfer materials of the fifth to seventhembodiment are prepared (see FIGS. 22E, 23F, and 24F). This transfermaterial is placed so that the side on which the component wiringpatterns are formed is brought into contact with a least one surface ofthe substrate so as to adhere thereto.

A step in which by peeling off first metal layer that is a carrier fromthe transfer material adhered to the base material sheet, the componentwiring pattern including at least the second metal layer and thecomponent pattern is transferred to the base material sheet. Thus, asubstrate in which components are incorporated is produced (see FIGS.22G, 23H, and 24H).

Thus, the fine wiring pattern and the component pattern including aninductor, a capacitor, and a resistor, and a semiconductor chip isformed on the base material sheet in flat form (see FIGS. 22G and 23H)or in a form of a concave shape (see FIG. 24H). Furthermore, in the thusproduced wiring substrate, when for example the wiring portion is in aconcave shape (FIG. 24H), the positioning of the wiring portion and thebump of the semiconductor chip can be carried out easily and theexcellent flip-chip mounting of the semiconductor is provided.

Twelfth Embodiment

Furthermore, the second method for producing the circuit substrate ofthe present invention is a method for producing a multi-layered circuitsubstrate shown in FIG. 25. In this production method, the substratecircuits (see FIGS. 22G, 23H, 24H, and the like) obtained in theeleventh embodiment are laminated in two layers or more.

Herein, numeral 2702 and 2709 denote a second metal layer forming awiring pattern, 2703 denotes a resistor, 2704 denotes a capacitor, 2705denotes an inductor, and 2706 denotes a base material sheet.

Since with this circuit substrate, a component pattern and a wiringpattern can be transferred and formed at low temperature of 100° C. orless, it is possible to maintain an uncured state not only in theceramic green sheet but also in the sheet using a thermosetting resin.Thus, the circuit substrate is laminated in two layers or more in anuncured state and then the laminate is heated and cured in oneoperation.

Therefore, in the multi-layered circuit substrate of four layers ormore, it is not necessary to correct the curing and shrinkage for eachlayer. Thus, it is possible to form a multi-layered circuit substratehaving a fine wiring pattern and a component pattern can be produced.However, the shape of the wiring portion and the component portionforming an inner layer is not necessarily concave but may be flat.Therefore, the circuit substrate etc. as shown in FIGS. 22G and 23H canbe used.

It is preferable in the production method described in the eleventhembodiment and this embodiment that the base material sheet includes aninorganic filler and a thermosetting resin, is provided with at leastone through hole and the through hole is filled with a conductive paste.Thus, it is possible to obtain a composite wiring substrate forhigh-density mounting, which has an excellent thermal conductivity andhas an IVH structure in which the wiring pattern is electricallyconnected to the conductive paste easily.

Furthermore, when the base material sheet is used, when the wiringsubstrate is formed, high temperature treatment is not required. Thiscan be performed sufficiently at about 200° C., i.e., the curingtemperature of the thermosetting resin.

The base material sheet preferably contains 70 to 95 weight % of aninorganic filler and 5 to 30 weight % of a thermosetting resin, and morepreferably contains 85 to 90 weight % of an inorganic filler and 10 to15 weight % of a thermosetting resin. Since the base material sheet cancontain inorganic fillers with a high concentration, by changing thecontent of inorganic fillers, the coefficient of thermal expansion,thermal conductivity, dielectric constant, and the like, can be setarbitrarily.

It is preferable that the inorganic filler includes at least oneinorganic filler selected from the group consisting of Al₂O₃, MgO, BN,AlN and SiO₂. By determining the kinds of inorganic filler properly, itis possible to set, for example, the coefficient of thermal expansion,thermal conductivity, and dielectric constant to the desirableconditions. For example, it is possible to set the coefficient ofthermal expansion of the base material sheet in the plane direction tobe substantially the same as the coefficient of thermal expansion of asemiconductor to be mounted, and to provide a high thermal conductivity.

The base material sheet using, for example, Al₂O₃, BN, AlN and the like,among the inorganic fillers, is excellent in thermal conductivity. Thebase material sheet using MgO is excellent in thermal conductivity andcapable of raising the constant of thermal expansion. Furthermore, whenSiO₂, particularly amorphous SiO₂ is used, a base material sheet havinga small constant thermal expansion, a light weight and low dielectricconstant can be obtained. Moreover, the inorganic filler can be usedsingly or by combination of two kinds or more of the inorganic fillers.

The base material sheet including the inorganic filler and thethermosetting resin composition can be produced by, for example, thefollowing method. First, a solution for adjusting the viscosity is addedinto a mixture including the inorganic filler and the thermosettingresin composition so as to prepare slurry having an arbitrary slurryviscosity. An example of the solvent for adjusting the viscosityincludes, for example, methyl ethyl ketone, toluene, and the like.

Then, the slurry is formed into a film on the preliminarily preparedmold release film by a doctor blade method, etc. and the film is treatedat a temperature below the curing temperature of the thermosetting resinso as to volatilize the solvent for adjusting the viscosity. Thereafter,the mold release film is removed, thereby producing a base materialsheet.

The thickness of the film at the formation is appropriately determinedby the amount of the solvent for adjusting viscosity to be added.Usually the thickness ranges from 80 to 200 μm. Furthermore, theconditions for volatilizing the solvent for adjusting viscosity isappropriately determined in accordance with the kinds of solvents foradjusting viscosity, kinds of thermosetting resins, or the like.However, usually, the volatilization is carried out at a temperature of70 to 150° C. for 5 to 15 minutes.

As the mold release film, usually, an organic film can be used. Forexample, it is preferable to use an organic film containing at least oneresin selected from the group consisting of, for example, polyethylene,polyethylene terephthalate, polyethylene naphthalate, polyphenylenesulfide (PPS), polyphenylene terephthalate, polyimide and polyamide, andmore preferably PPS.

Furthermore, another example of the base material sheet includes a sheetreinforcer impregnated with a thermosetting resin composition, andhaving at least one through hole filled with a conductive paste.

The sheet reinforcer is not particularly limited as long as it is aporous material capable of holding the thermosetting resin. However, itis preferable that the sheet reinforcer is at least one selected fromthe group consisting of a glass fiber woven fabric, a glass fibernon-woven fabric, a woven fabric of a thermal resistant organic fiberand a non-woven fabric of a thermal resistant organic fiber. An exampleof the thermal resistant organic fiber includes, for example, allaromatic polyamide (aramide resin), all aromatic polyester, polybutyleneoxide, and the like. In particular, aramide resin is preferable.

The thermosetting resin is not particularly limited as long as it has athermal resistance property. However, because of its excellent thermalconductivity, a resin containing at least one selected from the groupconsisting of an epoxy resin, a phenol resin, a cyanate resin and apolyphenylene phthalate resin. Furthermore, the thermosetting resin canbe used singly or by combination of two kinds or more of thethermosetting resins.

Such a base material sheet can be produced, for example, by immersingthe reinforcer sheet into the thermosetting resin composition, and thendrying to half-cured state.

It is preferable that the immersion is carried out so that the rate ofthe thermosetting resin with respect to the base material sheet is 30 to60 weight %.

It is preferable in the production method that when the base materialsheet containing a thermosetting resin is used, the wiring substratesare laminated by a heating and pressing treatment so as to cure thethermosetting resin. This can be performed sufficiently at about 200°C., i.e., the curing temperature of the thermosetting resin.

The reinforcer sheet may be a film such as polyimide, LCP, aramide etc.coated with the thermosetting resin.

On the other hand, the wiring substrate is not necessarily limited tothe resin substrate, and it may be a ceramic substrate. In this case, agreen sheet containing an organic binder, plasticizer, and ceramicpowder and having at least one through hole filled with the conductivepaste can be used as a base material sheet. This base material sheet hasa high thermal resistance, an excellent sealing property and excellentthermal conductivity.

The ceramic powder preferably contains at least one ceramic selectedfrom the group consisting of Al₂O₃, MgO, ZrO₂, TiO₂, BeO, BN, SiO₂, CaOand glass. More preferably, the ceramic powder is a mixture of 50 to 55weight % of Al₂O₃ and 45 to 50 weight % of glass powder. Moreover, theceramic can be used singly or in combination of two kinds or more ofthem.

An example of the binders to be used includes, for example, polyvinylbutyrate (PVB), acrylic resin, methyl cellulose resin, and the like. Anexample of the plasticizer includes, for example, butyl benzyl phthalate(BBP), dibutylphthalate (DBP), and the like.

Such a green sheet containing a ceramic can be produced by, for example,the same method as that for producing the base material sheet includingthe inorganic filler and the thermosetting resin. Moreover, the treatingconditions are appropriately determined by the kinds of the componentmaterials, etc.

For example, when the second metal layer 2403 of the transfer materialshown in FIG. 22, which is a wiring layer, is formed of silver, sincesilver has an oxidation resistant property, a binder removing processand firing in the air are possible. Thus, the production process becomeseasy. On the other hand, when the second metal layer 2503 and 2603 ofthe transfer materials shown in FIGS. 23 and 24 are formed of copper,the wiring portion to be transferred is a base metal that is likely tobe oxidized easily, the binder removing process in a non-oxidizationatmosphere, for example in an nitrogen atmosphere, or nitrogen firingprocess is required. Therefore, the green sheet is required to have aconfiguration corresponding to the nitrogen process. Furthermore, alsovehicle and binder used for printing of the inductor, capacitor, andresistor, are strongly required to have a thermal deposition propertyunder the non-oxidation atmosphere.

The thickness of the base material sheet is usually 100 to 250 μm.

It is preferable that the base material sheet has at least one throughhole and the through hole is filled with a conductive paste. Theposition of the through hole is not particularly limited as long as thethrough hole is formed so that it is in contact with the wiring pattern.However, it is preferable that through holes are positioned at equalintervals of 250 to 500 μm pitch.

The size of the through hole is not particularly limited, but usually,the diameter is 100 to 200 μm, and more preferably 100 to 150 μm.

The method for forming through holes is appropriately determined inaccordance with the kinds of the base material sheet, etc. However, thepreferable example of the method includes, for example, a carbon dioxidegas laser process, a process with a punching machine, a bulk processwith a mold, and the like.

The conductive paste is not particularly limited as long it hasconductivity. However, usually, a resin containing a particulateconductive metal, and the like, can be used. An example of theconductive metal material to be used includes, for example, copper,silver, gold, silver-palladium, and the like. An example of thethermosetting resin includes an organic binder of, for example, an epoxyresin, a phenol resin, a cellulose resin, an acrylic resin, and thelike.

The amount of the conductive metal material in the conductive paste isusually 80 to 95 weight %. Furthermore, when the base material sheet isa green sheet, thermal plasticizer binder is used instead ofthermosetting, and glass powder is used as an adhesive agent.

Next, the method for adhering the transfer material to the base materialsheet and the method for peeling off the first metal layer from thesecond metal layer are not particularly limited. However, when the basematerial sheet includes a thermosetting resin, for example, the adheringmethod and the peeling method can be carried out as follows.

First, the transfer material (FIG. 23F) and the base material sheet 2508are placed as shown in FIG. 23G, and heated and pressed so as to fuseand soften the thermosetting resin in the base material sheet, thusallowing the metal layer 2503 having a wiring patterns and passivecomponent patterns 2505, 2506, and 2507 to be embedded in the basematerial sheet. Herein, numeral 2505 denotes an inductor, 2506 denotes acapacitor, and 2507 denotes a resistor. However, it is preferable thatwhen a circuit component such as a capacitor that needs to haveelectrodes on both surfaces of the dielectric layer is transferred, onlythe wiring pattern 2510 corresponding to the wiring pattern ispreliminarily formed on the base material sheet 2508 preliminarily (seeFIG. 23G,).

Then, the base material sheet on which the transfer material is pressedis treated at a softening temperature or a curing temperature of thethermosetting resin. In the latter case, the resin is cured, whichallows the adhesion between the transfer material and the base materialsheet and the adhesion between the second metal layer 2503 and the basematerial sheet 2508 to be fixed.

The conditions for heating and pressing treatment are not particularlylimited as long as the thermosetting resin is not perfectly cured.However, the heating and pressing usually can be carried out under thepressure of 9.8×10⁵ to 9.8×10⁶ Pa (10 to 100 kgf/cm²), at thetemperature of 70 to 260° C. for 30 to 120 minutes.

Then, after the transfer material (FIG. 23F) and the sheet substrate2508 are adhered to each other, for example, the first metal layer 2501that is the carrier layer is pulled so as to peel it off with thepeeling layer. Thus, the first metal layer 2501 can be peeled off fromthe second metal layer 2503 and the passive component 2505, 2506 and the2507.

Namely, since the adhesive strength between the first metal layer andthe second metal layer via the peeling layer is weaker than the adhesivestrength between the base material sheet and the second metal layer thatis a wiring layer, the adhering surface between the first metal layerand the second metal layer is peeled off, and only the second metallayer is transferred to the base material sheet while the first metallayer is peeled off (see FIG. 23H).

Curing of the thermosetting resin may be carried out after the firstmetal layer is peeled off from the component wiring pattern.

On the other hand, when the base material sheet is a green sheet formingthe ceramic substrate, the following method can be employed. Forexample, in FIGS. 22A to 22D, a copper foil is used for the first metallayer, and silver wiring is formed for the second metal layer 2403 thatis a wiring layer. Thereafter, a passive component etc. is formed by ascreen printing method for electrically connecting the silver wiring,thus forming a component for transfer and a wiring pattern. However,since in the case of the ceramic substrate, firing also is carried out,the semiconductor chip as shown in FIG. 22E′ is not mounted. By carryingout the same heating and pressing treatment as mentioned above, thecomponent wiring pattern is allowed to be embedded in the green sheetthat is a base material sheet and to adhere the green sheet and thecomponent wiring pattern for transfer.

Thereafter, as mentioned above, by peeling the carrier, the componentmaterial other than the component wiring pattern is removed. Then, onthe green sheet on which the component wiring pattern is transferred, analumina green sheet for constraint is laminated. Thereafter, the binderremoving process and the sintering treatment are carried out in the air,thus to sinter the ceramic and to fix the transferred second metal layerand the component pattern onto the ceramic substrate. Since the transfermaterial has a wiring pattern made of silver, it is advantageous thatthe binder removing process and the firing can be carried out in theair.

On the other hand, in the case of the methods shown in FIGS. 23A to 23H,and the FIGS. 24A to 24H, the first metal layer is formed of a copperfoil, and a copper wiring is formed as the second metal layer, that is,a wiring layer is formed by a chemical etching process using thephotolithography. The copper wiring can be produced more cheaply thanthe silver wiring produced by plating, and is excellent in migrationresistance property. Thereafter, a passive component etc. is formed by ascreen printing method for electrically connecting to the copper wiring.Thus, the component wiring pattern for transfer is produced.

However, since in the case of the ceramic substrate, firing also iscarried out, the semiconductor chip as shown in FIG. 22E′ is notmounted. By carrying out the same heating and pressing treatment asmentioned above, the component wiring pattern is allowed to be embeddedin the green sheet that is a base material sheet and to adhere the greensheet and the component wiring pattern for transfer.

Thereafter, as mentioned above, by peeling the carrier, the componentmaterial other than the component wiring pattern is removed.

Then, on the green sheet to which the component wiring pattern istransferred, an alumina green sheet for constraint is laminated.Thereafter, in such an atmosphere in which copper is not oxidized, forexample, nitrogen atmosphere, a binder removing process and firing arecarried out, thereby sintering the ceramic. Thereby, the transferredsecond metal layer and wiring pattern are allowed to be fixed on theceramic substrate. Since this transfer material has a wiring made ofcopper, transfer itself can be produced cheaper that the silver wiring.However, it is necessary to carry out the firing process in anon-oxidization atmosphere by taking the copper wiring into account.

Therefore, both for a binder for green sheet and a binder for a pasteforming a passive component, it is necessary to use a binder having anexcellent thermal decomposition property such as, for example,methacrylate based acrylic binder, etc.

Therefore, the transfer materials are used in different ways inaccordance with sintering conditions of a green sheet that forms asubstrate or the ceramic forming the passive component.

The conditions for heating and pressing treatment can be determinedappropriately. However, the heating and pressing usually can be carriedout under the pressure of 9.8×10⁵ to 9.8×10⁷ Pa (10 to 200 kgf/cm²), atthe temperature of 70 to 100° C. for 2 to 30 minutes. Therefore, awiring pattern can be formed without damaging the green sheet.

The conditions for the treatment for removing the binder isappropriately determined in accordance with the kinds of binders, metalforming the wiring pattern, or the like. However, usually, the treatmentis carried out by the electric furnace under the conditions of atemperature of 500 to 700° C., temperature rising time of 10 hours, andmaintaining time of 2 to 5 hours.

The conditions for firing are appropriately determined in accordancewith the kinds of the ceramic and the like. However, usually, the firingis carried out in a belt furnace, at a temperature of 860 to 950° C. for30 to 60 minutes in the air or in nitrogen.

Furthermore, the second method for producing the wiring substrate willbe explained. When the multi-layered circuit substrate as shown in FIG.25 is produced, single layered circuit substrates laminated sequentiallyas mentioned above, and interlayer portion is adhered. Needless to say,it is possible to harden two or more of single layered circuitsubstrates in one operation.

For example, when the circuit substrate having a base material sheetincluding a thermosetting resin is laminated, respectively as shown inFIGS. 26A to 26C, similar to the above, by transferring only thecomponent wiring pattern to the base material sheet, a single layeredcircuit substrate as shown in FIGS. 26A′ to 26C′ can be obtained. Thelaminate of the single layered circuit substrates is heated and pressedat the curing temperature of the thermosetting resin so as to cure thethermosetting resin, thus to fix the adhesion between the circuitsubstrates.

When the heating and pressing temperature for transferring the wiringlayer in the single layer wiring substrate is set to be 100° C.intentionally, even after the transfer, the base material sheet can beused as a prepreg. Thus, it is possible to produce a multi-layeredwiring substrate by fixing the adhesion between the substrates after thesingle layer wiring substrates are laminated instead of sequentiallylaminating the single layer wiring substrates.

Furthermore, for example, in the case of laminating the ceramic circuitsubstrate having a base material sheet including a ceramic, similar tothe above, after only the component wiring pattern is transferred to thebase material sheet, this single layered ceramic circuit substrate islaminated and heated and pressed. Thus, firing of the ceramic and theadhesion fixation between the circuit substrates can be carried out atthe same time.

The number of the laminated layers in the multi-layered circuitsubstrates (FIG. 25) is not particularly limited. However, the number isusually 4 to 10 layers, and as many as 12 layers is also possible.Furthermore, the total thickness of the multi-layered circuit substrateis usually 500 to 1000 μm.

The surface of the circuit substrates forming inside layers other thanthe outermost layer of the multi-layered circuit substrate (FIG. 25) maybe flat instead of a convex and concave portion in which the wiringpattern is embedded in its concave portion by taking the electricconnection structure by inner via into account. In order to obtain thisstructure intentionally, the use of the fourth or fifth transfermaterial is one solution. Furthermore, the outer most layer of themulti-layered substrate may be a flat circuit substrate, the surface ofwhich is flat. However, if the surface has a concave portion, and thesecond metal layer etc. is formed in the bottom of the concave portionin the wiring substrate, it is possible to mount a semiconductor chipetc. as shown in FIG. 24H more easily.

Example

Hereinafter, the fifth to twelfth embodiments of the present inventionwill be described in detail by way of Examples.

Example 11

FIGS. 22A to 22G′ are cross-sectional views schematically showing oneexample of a process for producing the fourth transfer material of thepresent invention.

As shown in FIGS. 22A to 22E and FIGS. 22A to 22E′, a transfer materialincluding passive components 2405, 2406 and 2407 (FIG. 22E), and atransfer material including a semiconductor chip that is an activecomponent 2408 (FIG. 22E′) were produced.

As shown in FIG. 22A, as a first metal layer 2401, an electrolyticcopper foil having a thickness of 35 μm was prepared. First, a coppersalt raw material was dissolved in an alkaline bath and allowed to beelectrodeposited to a rotation drum so that it had a high electriccurrent density. Thus, a metal layer (copper layer) was formed. Thiscopper layer was rolled up continuously so as to form an electrolyticcopper foil.

Next, as shown in FIG. 22B, a pattern opposite to the wiring pattern wasformed by using a dry film resist 2404. Thereafter, as shown in FIG.22C, a metal layer for forming a wiring pattern made of silver 2403 waslaminated by electrolytic plating on the first metal layer 2401 in athickness of 9 μm. Thus, two-layered structure as shown in FIG. 22D wasproduced. The surface thereof was subjected to a roughening treatment sothat the average roughness (Ra) of the center line of the surface wasabout 4 μm.

Next, the portion corresponding to the passive components (inductor,capacitor, and resistor) were formed by a screen printing method. In aconfiguration of this Example, the passive components capable of beingsintered together were employed so that they are mounted on a ceramicsubstrate.

As the inductor 2405, a paste was formed by kneading a Ni—Zn ferritepowder, 5 weight % of acrylic resin (Kyoeisya Kagaku Co., Ltd.;polymerization degree 100 cps), 15 weight % of terpineol (manufacturedby Kanto Chemical Co., Inc), and 5 weight % of BBP (manufactured byKanto Chemical Co., Inc) by using a triple roller.

As the capacitor 2406, similarly, a paste was formed by kneadingPb-based perovskite compound (PbO—MgO—Nb₂O₅—NiO—WO₃—TIO₂) powder byusing a triple roller. As the resistor 2407, similarly, a paste wasformed by mixing 5 to 50 weight % of ruthenium oxide powder with 95 to50 weight % of low melting point borosilicate glass.

The inductor 2405, capacitor 2406, and resistor 2407 formed of thesepastes were produced on the two layered structure shown in FIG. 22D by aprinting method by using a predetermined shaped mask as shown in FIG.22E. After printing, they were dried at 90° C. for 20 minutes.

When the transfer, firing and fixation were carried out on the ceramicsubstrate, an active component such as semiconductor chip, etc. was notformed on the transfer material (see FIG. 22E). However, when thetransfer is carried out on the resin substrate, an active component suchas semiconductor chip 2408 etc. can be formed (see FIG. 22E′). Afterflip-chip mounting, an underfill 2411 may be used for sealing a gapbetween a semiconductor chip 2408 and a wiring pattern 2412 andcompletely cured for integration at 150° C.

By using the transfer material shown in FIG. 22E, as shown in FIGS. 22Fto 22G, a ceramic circuit component was produced.

First, a substrate 2409 on which a wiring pattern is transferred wasprepared. This substrate 2409 was produced by preparing a lowtemperature sintering ceramic green sheet A including a low temperaturesintering ceramic material and an organic binder, providing thesubstrate 2409 with via holes, and filling the via holes with aconductive paste 2410. Hereinafter, the component compositions of thegreen sheet A are described.

(Component Composition of the Green Sheet A)

-   -   mixture of ceramic powder Al₂O₃ and borosilicate glass (MLS-1000        manufactured by Nippon Electric Glass Co., Ltd.) 88 weight %    -   carboxylic acid based acrylic binder (Olicox, Kyoeisya Kagaku        Co., Ltd.) 10 weight %    -   BBP (manufactured by Kanto Chemical Co., Inc.) 2 weight %

Each of the above-mentioned component was weighed so as to have theabove-mentioned composition weight ratio. A solvent of toluene was addedinto the mixture of the above-mentioned components so that the viscosityof the slurry mixture was about 20 Pa·s, and then rotated and mixed byusing alumina balls in a pot at the rotation rate of 500 rpm for 48hours so as to form into a slurry.

Next, as a mold release film, PPS film having a thickness of 75 μm wasprepared. On the PPS film, the slurry was formed into a film sheet bythe doctor blade method at a gap of about 0.4 mm. The toluene solvent inthe sheet was allowed to volatilize so as to remove the PPS film, thusto form a green sheet A having a thickness of 220 μm. Since in thisgreen sheet A a plasticizer BBP was added into the carboxylic acid basedacrylic binder, this sheet had high strength, flexibility and excellentthermal decomposition property.

This green sheet A was cut in a predetermined size by the use of itsflexibility, and provided with through holes (via holes) having adiameter of 0.15 mm at equally intervals with a pitch of 0.2 to 2 mm byusing a punching machine. Then, the through holes were filled with aconductive paste for filling via holes by a screen printing method.Thus, the substrate 2409 was produced. The conductive paste 2410 to beused was obtained by kneading the following materials at the followingcompositions by using a triple roller.

[Conductive Paste 2410]

-   -   spherical silver particles (Mitsui Mining & Smelting Co., Ltd.,        particle diameter of 3 μm) 75 weight %    -   acrylic resin (manufactured by Kyoeisya Kagaku Co., Ltd.,        polymerization degree 100 cps) 5 weight %    -   terpineol (manufactured by Kanto Chemical Co., Inc.) 15 weight %    -   BBP (manufactured by Kanto Chemical Co., Inc.) 5 weight %

Next, as shown in FIG. 22F, the transfer material produced in Example22E was placed so that it was brought into contact with both surfaces ofthe substrate 2409, and a heating and pressing treatment was carried outby a thermal press method at a pressing temperature of 70° C. and apressure of about 5.88×10⁶ Pa (60 kgf/cm²) for 5 minutes. Herein, in thecapacitor 2406, an electrode pattern 2411 may be formed previously onthe substrate 2409 by a transfer method etc. so that the dielectriclayer was sandwiched between the upper and lower sides of the electrodesurface. This method is possible only with the transfer material of thepresent invention on which the capacitor is formed by printing and wasnot possible in the conventional method in which the dielectric layerwas printed on the substrate green sheet.

With this heating and pressing treatment, an acrylic resin in thesubstrate 2409 was fused and softened. Thus, the wiring layer 2403 ofthe second metal layer and circuit components 2405, 2406 and 2407 wereembedded into the substrate 2409.

After the laminate of this substrate 2409 and the transfer material wascooled, the first metal layer 2401 that is a carrier of transfermaterial was peeled off from the laminate, and thereby a circuitsubstrate sheet, on both surfaces of which the wiring layer 2403 and thecircuit components 2405, 2406 and 2407 were transferred, was obtained.

Then, the circuit substrate sheet was sandwiched by an alumina greensheet formed of an alumina inorganic filler that is not sintered at thefiring temperature so as to form a laminate, and the laminate wassubjected to a binder removing process and firing in the air, andthereby fixed. First, in order to remove the organic binder in thecircuit substrate (FIG. 22G), the laminate was heated by an electricfurnace up to 500° C. at the raising temperatures at 25° C./hour,treated at 500° C. for 2 hours. Then, the wiring substrate in which thebinder was removed was burned at 900° C. for 20 minutes in the air. Thefiring conditions were set to be a temperature rising time of 20minutes, temperature falling time of 20 minutes and in/out total time of60 minutes. After firing, the alumina green sheet was easily removed.

This wiring substrate had a flat mounted surface after firing. On thewiring layer 2403 of this circuit substrate (FIG. 22G), a gold platinglayer may be formed.

Warp, cracks, distortion did not occur in this circuit substrate. Thisis partly because a non-shrinkage sintering process was used in a planedirection. This process made it possible to burn the copper foil wiringand ceramic substrate simultaneously. The mounting position of each ofthe circuit components (inductor, capacitor and resistor) was accurate.Thus, a precise circuit substrate as designed was produced in onetransfer.

Furthermore, when capacitor high temperature load reliability test (125°C., 50 V, 1000 hours) was carried out, the insulating resistance of thedielectric layer of the capacitor 2406 was not deteriorated and 10⁶Ω ormore of insulating resistance was secured. Furthermore, the dielectricconstant was 5000 for the dielectric layer, and 8.1 for the substratelayer. An inductance of the inductor 2405 was secured to be 0.5 μH.Furthermore, the resistance value of the resistor 2407 was permitted tobe a desired value ranging from 100Ω to 1 MΩ.

Thus, the use of the transfer material of the present inventionfacilitated formation of circuit components including passive componentssuch as an inductor, a capacitor, and a resistor, etc.

In addition, it is advantageous in the present invention that by anon-shrinkage sintering process in the plane direction and a transferprocess of a high-density conductive pattern by plating, a wiring havingan extremely high dielectric constant can be attained and that by usingsilver for the wiring metal, a binder removing process and firing can beperformed in the air. In particular, since the latter process can beemployed, the composition of a substrate, each composition of passivecomponents such as an inductor, a capacitor, and resistor, etc, can beselected from the wide range.

FIGS. 22F′ and 22G′ show the case where the transfer material shown inFIG. 22E′ is transferred, mounted and fixed to a resin substrate. As inthe case of the ceramic green sheet, it was confirmed that transfer andmounting were carried out in one time.

Example 12

FIGS. 23A to 23H are cross-sectional views schematically showing oneexample of a process for producing a wiring substrate by using the fifthtransfer material.

The fifth transfer material was produced by the way shown in FIGS. 23Ato 23F.

First, as shown in FIG. 23A, as a first metal layer 2501, anelectrolytic copper foil having a thickness of 35 μm was prepared.Specifically, a copper salt raw material was dissolved in an alkalinebath and allowed to be electrodeposited to a rotation drum so that ithad a high electric current density. Thus, a metal layer (copper layer)was formed. This copper layer was rolled up continuously so as to forminto an electrolytic copper foil.

Next, a thin nickel-phosphorous alloy plating layer was formed on thesurface of the first metal layer 2501 as a peel layer 2502. As a metallayer for forming a wiring pattern 2503, an electrolytic copper foilthat is the same as the first metal layer 2501 was laminated in athickness of 9 μm by electrolytic plating, to thus form the second metallayer 2503. Thus, a three-layered laminate was produced (FIG. 23A).

The surface of the laminate was subjected to a roughening treatment sothat the average roughness (Ra) of the center line of the surface wasabout 4 μm. The roughening treatment was carried out by precipitatingfine copper powder on the electrolytic copper foil.

Next, a dry film resist (DFR) 2504 was placed on the laminate byphotolithography as shown in FIG. 23B, and exposure and development ofthe wiring pattern portion were carried out as shown in FIG. 23C.Thereafter, the second metal layer 2503 of the laminate was etched by achemical etching process (immersing in an aqueous solution of ferricchloride) so as to form a desired wiring pattern as shown in FIG. 23D.With such an etchant, only the second metal layer was etched and thethin nickel-phosphorous alloy layer that is the peel layer was notetched.

Thereafter, as shown in FIG. 23E, the remaining dry film resist wasremoved by a peeling agent. Thus, a transfer material was obtained.

Next, the portion corresponding to the passive components was formed bya screen printing method. In a configuration of this Example, thepassive components capable of being sintered together were employed sothat they are mounted on a ceramic substrate.

As the inductor 2505, a paste was formed by kneading Ni—Zn ferritepowder, 5 weight % of acrylic resin (Kyoeisya Kagaku Co., Ltd.;polymerization degree: 100 cps), 15 weight % of terpineol (manufacturedby Kanto Chemical Co., Inc), and 5 weight % of BBP (manufactured byKanto Chemical Co., Inc) by using a triple roller.

As the capacitor 2506, similarly, a paste was formed by kneadingPb-based perovskite compound (PbO—MgO—Nb₂O₅—NiO—WO₃—TIO₂) powder byusing a triple roller.

As the resistor 2507, similarly, a paste was formed by mixing 5 to 50weight % of ruthenium oxide powder with 95 to 50 weight % of low meltingpoint borosilicate glass.

By using these pastes, by using a predetermined shaped mask, theinductor 2505, capacitor 2506, and resistor 2507 were formed on thetransfer material shown in FIG. 23E by a printing method as shown inFIG. 23F. By using the transfer materials, a ceramic substrate wasproduced by the method shown in FIGS. 23G to 23H.

First, a substrate 2508 was prepared. This substrate 2508 was producedby preparing a low temperature sintering ceramic green sheet B includinga low temperature sintering ceramic material and an organic binder,providing the substrate 2508 with via holes, and filling the via holeswith a conductive paste 2509. Hereinafter, the component compositions ofthe green sheet B are described.

[Component Composition of the Green Sheet B]

-   -   mixture of ceramic powder Al₂O₃ and borosilicate glass (MLS-1000        manufactured by Nippon Electric Glass Co., Ltd.) 88 weight %    -   methacrylic acid based acrylic binder (Olicox 7025, Kyoeisya        Kagaku Co., Ltd.) 10 weight %    -   BBP (manufactured by Kanto Chemical Co., Inc.) 2 weight %

Each of the above-mentioned component was weighed so as to have theabove-mentioned composition weight ratio. A solvent of toluene was addedinto the mixture of the above-mentioned components so that the viscosityof the slurry mixture was about 20 Pa·s, and then rotated and mixed byusing alumina balls in a pot at the rotation rate of 500 rpm for 48hours so as to form into a slurry.

Next, as a mold release film, a PPS film having a thickness of 75 μm wasprepared. On the PPS film, the slurry was formed into a film sheet bythe doctor blade method at a gap of about 0.4 mm. The toluene solvent inthe sheet was allowed to volatilize so as to remove the PPS film, thusto form a green sheet B having a thickness of 220 μm. Since in thisgreen sheet B, a plasticizer BBP was added into the methacrylic acidbased acrylic binder that is an organic binder, this sheet hadflexibility and an excellent thermal decomposition property.

This green sheet B was cut in a predetermined size by the use of itsflexibility, and provided with through holes (via holes) having adiameter of 0.15 mm at equally intervals with a pitch of 0.2 to 2 mm byusing a punching machine. Then, the through holes were filled with aconductive paste 2509 for filling via holes by a screen printing method.Thus, the substrate 2508 was produced by the above-mentioned process.The conductive paste 2509 to be used was obtained by kneading thefollowing materials at the following compositions by using a tripleroller.

[Conductive Paste 2509]

-   -   spherical silver particles (Mitsui Mining & Smelting Co., Ltd.,        particle diameter of 3 μm) 75 weight %    -   acrylic resin (manufactured by Kyoeisya Kagaku Co., Ltd.,        polymerization degree 100 cps) 5 weight %    -   terpineol (manufactured by Kanto Chemical Co., Inc.) 15 weight %    -   BBP (manufactured by Kanto Chemical Co., Inc.) 5 weight %.

Next, the transfer material produced as mentioned above (FIG. 23F) wasplaced so that it was brought into contact with both surfaces of thesubstrate 2508, and a heating and pressing treatment was carried out bya thermal press at a pressing temperature of 70° C. and a pressure ofabout 5.88×10⁶ Pa (60 kgf/cm²) for 5 minutes. Herein, in the capacitor2506, an electrode pattern 2510 may be formed previously on thesubstrate 2508 by a transfer method etc. so that the dielectric wassandwiched between the upper and lower sides of the electrode surfaces.This method is possible only with the transfer material of the presentinvention on which the capacitor is formed by printing and was difficultin the conventional method in which the dielectric layer was printeddirectly on the substrate green sheet.

With this heating and pressing treatment, an acrylic resin in thesubstrate 2508 was fused and softened. Thus, the second metal layer 2503that is a wiring pattern and circuit components (the inductor 2505, thecapacitor 2506, and the resistor 2507) were embedded into the substrate2508.

After such a laminate of the transfer material and this substrate 2508was cooled, the first metal layer 2501 that is a carrier was peeled offfrom the laminate, thereby a circuit substrate sheet both surfaces ofwhich the second metal layer 2503 that is a wiring pattern and thecircuit components (the inductor 2505, the capacitor 2506, and theresistor 2507) were transferred was obtained.

Then, the circuit substrate sheet was sandwiched by an alumina greensheet formed of only an alumina inorganic filler, which is not sinteredat the firing temperature of the substrate so as to form a laminate, andthe laminate was subjected to a binder removing process and firing in anatmosphere of nitrogen, and thereby fixed.

First, in order to remove the organic binder in the circuit substrate(FIG. 23H), the laminate was heated by an electric furnace up to 600° C.with raising temperatures at 25° C./hour, and treated at 600° C. for 2hours. Then, the wiring substrate in which the binder was removed wasburned at 900° C. for 20 minutes by a belt furnace in an atmosphere ofnitrogen. The firing condition was set to be a temperature rising timeof 20 minutes, temperature falling time of 20 minutes and in/out totaltime of 60 minutes. After firing, the alumina green sheet was easilyremoved.

This wiring substrate (FIG. 23H) had a flat mounted surface. On thewiring layer 2503 of this circuit substrate (FIG. 23H), a gold platinglayer may be formed.

Warp, cracks, distortion did not occur in this circuit substrate. Thisis partly because a non-shrinkage sintering process was used in a planedirection. This made it possible to burn the copper foil wiring andceramic substrate simultaneously. Also, the mounting position of eachcircuit component was accurate. Thus, a precise circuit substrate asdesigned was produced in one transfer.

Furthermore, when capacitor high temperature load reliability test (125°C., 50V, 1000 hours) was carried out, the insulating resistance of thedielectric layer of the capacitor 2506 was not deteriorated and the 10⁶Ωor more of insulating resistance was secured. Furthermore, thedielectric constant was 5000 for the dielectric layer, and 8.1 for thesubstrate layer. An inductance of the inductor 2505 was secured to be0.5 μH. Furthermore, the resistance value of the resistor 2507 could bea desired value ranging from 100Ω to 1 MΩ.

Thus, the use of the transfer material of the present inventionfacilitated formation of circuit components including an inductor, acapacitor, and a resistor, etc.

Example 13

FIGS. 24A to 24H are cross-sectional views schematically showing oneexample of a process for producing a wiring substrate by using the sixthtransfer material.

The sixth transfer material was produced by a method shown in FIGS. 24Ato 24H.

First, as a first metal layer 2601, an electrolytic copper foil having athickness of 35 μm was prepared. A copper salt raw material wasdissolved in an alkaline bath and allowed to be electrodeposited to arotation drum so that it had a high electric current density. Thus, ametal layer (copper layer) was formed. This copper layer was rolled upcontinuously so as to form into an electrolytic copper foil.

Next, an adhesive agent formed of an organic layer was applied thinly onthe surface of the first metal layer 2601 as a peel layer 2602. As asecond metal layer 2603 for forming a wiring pattern, an electrolyticcopper foil same as the first metal layer 2601 was laminated in athickness of 9 μm by electrolytic plating. Thus, three-layered laminatewas produced (FIG. 24A).

The surface of the laminate was subjected to a roughening treatment sothat the average roughness (Ra) of the center line of the surface wasabout 4 μm. The roughening treatment was carried out by precipitatingfine copper powder on the electrolytic copper foil.

Next, as shown in FIG. 24B, a dry film resist (DFR) 2604 was placed onthe laminate by photolithography and exposure and development of thewiring pattern portion was carried out as shown in FIG. 24C. Thereafter,as shown in FIG. 24D, not only the second metal layer 2602 but also thesurface portion of the first metal layer 2601 of the laminate wereetched by a chemical etching process (immersing in an aqueous solutionof ferric chloride) so as to form a desired wiring pattern.

Thereafter, the DFR 2604 was peeled off by a peeling agent so as toproduce a three-layered structure shown in FIG. 24E. Since the firstmetal layer and the second metal layer are formed of the same metal,copper, it is possible to form a convex portion on not only the secondmetal layer but also a part of the first metal layer. This structure ischaracterized in that the wiring pattern is processed also in the firstmetal layer that is a carrier layer. Moreover, in this example, as thepeel layer, an organic layer was used. The peel layer is not necessarilylimited thereto, and for example, a nickel plating layer etc. may beused. In this case, the transfer material having the same effect can beobtained.

In this three-layered structure, the peel layer 2602 that adheres thefirst metal layer 2601 to the second metal layer 2603 for forming thewiring pattern was weak in adhesive strength itself but excellent inetch resistance property. Thus, even if the entire three-layeredstructure was subjected to an etching process, the wiring pattern wasformed without peeling of the interlayer portion. The adhesive strengthbetween the first metal layer 2601 and the second metal layer 2603 viathe peel layer 2602 was 40 N/m (gf/cm), exhibiting an excellent peelingproperty.

Next, a circuit component was formed by a screen printing method. In aconfiguration of this Example, the passive components capable of beingsintered together were employed so that they are mounted on a resinsubstrate

As the inductor 2605, a paste was formed by kneading a Ni—Zn ferritepowder, 10 weight % of liquid epoxy resin (EF-450 manufactured by NipponRec Co. Ltd.), 0.3 weight % of coupling agent (46B, titanate basedcoupling agent manufactured by Ajinomoto Co., Inc.) by using a kneaderrevolving both on its orbital and on its own axis at high speed.

Moreover, a paste including magnetic alloy powder, was sendust powder asa filler was produced. As the capacitor 2606, similarly, a paste wasformed by kneading Pb-based perovskite compound(PbO—MgO—Nb₂O₅—NiO—WO₃—TIO₂) powder by using a triple roller. As theresistor 2607, similarly, a paste was formed having the similarconfiguration with the content of carbon content by varying the contentof carbon.

The sixth transfer material was produced by using the circuit componentsformed of these pastes were produced on the three-layered structureshown in FIG. 24E by a printing method by using a predetermined shapedmask as shown in FIG. 24F. After printing, they were dried at 90° C. for20 minutes.

Moreover, on the transfer material, a wiring pattern 2613 was formed sothat a semiconductor chip 2608 is mounted on the wiring substrate aftertransfer by using the transfer material.

Thereafter, as shown in FIGS. 24G to 24H, a print circuit substrate wasproduced as follows.

First, a substrate 2610 was prepared. This substrate 2601 was producedby preparing a base material sheet formed of a composite material,providing the substrate 2601 with via holes, and filling the via holeswith a conductive paste 2611. Hereinafter, the component compositions ofthe base material sheet 2610 are described.

[Component Composition of the Substrate Sheet 2610]

-   -   Al₂O₃ (AS-40 manufactured by Showa Denko K. K., average particle        diameter of 12 μm) 90 weight %    -   liquid epoxy resin (EF-450, manufactured by Nippon Rec Co. Ltd.)        9.5 weight %    -   carbon black (manufactured by Toyo Carbon) 0.2 weight %    -   coupling agent (46B, titanate based coupling agent manufactured        by Ajinomoto Co., Inc.) 0.3 weight %

Each of the above-mentioned components was weighed so as to have theabove-mentioned composition weight ratio. A solvent of methyl ethylketone as a solvent for adjusting viscosity was added into the mixtureof the above-mentioned components so that the viscosity of the slurrymixture was about 20 Pa·s, and then rotated and mixed by using aluminaballs in a pot at the rotation rate of 500 rpm for 48 hours so as toform into a slurry.

Next, as a mold release film, a PET film having a thickness of 75 μm wasprepared. On the PET film, the slurry was formed into a film sheet at agap of about 0.7 mm by a doctor blade method. The film sheet was allowedto stand for 1 hour at 100° C. so as to volatilize the methyl ethylketone solvent and to remove the PET film, thus to form into a basematerial sheet 2601 having a thickness of 350 μm. Since the solvent wasremoved at 100° C., the epoxy resin was kept uncured and the basematerial sheet had a flexibility.

This base material sheet was cut in a predetermined size by the use ofits flexibility, and provided with through holes (via holes) having adiameter of 0.15 mm at equally intervals with a pitch of 0.2 to 2 mm.Then, the through holes were filled with a conductive paste 2611 forfilling via holes by a screen printing method. Thus, the substrate 2610was produced. The conductive paste 2611 to be used was obtained bymixing and kneading the following materials at the below mentionedcompositions by using a triple roller.

[Conductive Paste 2611]

-   -   spherical copper particles (Mitsui Mining & Smelting Co., Ltd.,        particle diameter of 2 μm) 85 weight %    -   bisphenol A epoxy resin (Epicoat 828 manufactured by Yuka Shell        Epoxy) 3 weight %    -   glycidyl ester based epoxy resin (YD-171 manufactured by Toto        Kasei) 9 weight %    -   amine adduct hardening agent (MY-24 manufactured by Ajinomoto        Co., Inc.) 3 weight %

Next, as shown in FIG. 24G, the transfer material was placed so that thetransfer material produced in the above (FIG. 24F) was brought intocontact with both surfaces of the substrate 2610, heated and pressed bya thermal press at a pressing temperature of 120° C. and a pressure of9.8×10⁵ Pa (10 kgf/cm²) for 5 minutes.

In the capacitor 2610, when the dielectric layer is sandwiched betweenthe upper and lower electrodes, an electrode pattern 2612 can betransferred to the substrate previously. Such a method is possible onlywith the transfer material of the present invention on which thecapacitor is formed by printing and was difficult in the conventionalmethod in which the dielectric layer was printed on the composite sheetincluding a ceramic as a filler.

With this heating and pressing treatment, an epoxy resin in thesubstrate 2610 (an epoxy resin in the base material sheet and theconductive paste 2611) was fused and softened (FIG. 24H). Thus, thecircuit components pattern (the inductor 2605, the capacitor 2606, andthe resistor 2607) and the second metal layer 2603 as a wiring patternwere embedded in the substrate 2610. The heating temperature was furtherraised and treated at 175° C. for 60 minutes, thereby the epoxy resinwas cured. Thereafter, a semiconductor chip 2608 was flip-chip mountedon the wiring 2613.

Thus, the base material sheet was adhered to the entire circuitcomponent pattern strongly. Furthermore, the conductive paste 2611 andeach of the circuit components was electrically connected (inner viaconnection) and adhered to each other strongly.

Thereafter, a first metal layer 2601 that is a carrier layer and thepeel layer 2602 were peeled off, thereby a wiring substrate bothsurfaces of which had a circuit component patterns (inductor 2605,capacitor 2606, and resistor 2607) and wiring patterns (second metallayer 2603) was obtained. On the surfaces of the wiring substrate, theconcave portion corresponding to the depth of the etched portion of thefirst metal layer 2603 was formed in the transfer material, and all thewiring patterns and the circuit component patterns were formed at thebottom of the concave portion.

Thus, the use of this transfer material facilitated peeling of theadhesive plane between the first metal layer 2601 and the second metallayer 2603 via the peel layer 2602, and enabled transfer of only thesecond metal layer 2603 and circuit component patterns (inductor 2605,capacitor 2606, and resistor 2607) to the substrate when the secondtransfer 2603 was transferred to the substrate 2610.

In this Example, the first metal layer 2601 that is a carrier layer wasformed of a copper foil having a thickness of 35 μm, and even if thetransfer material of the substrate 2610 was deformed at the time oftransfer, the carrier layer was resistant to the deformation stress. Onthe other hand, in the transfer material in this example, the wiringportion has a convex shape, when the transfer material is pressed ontothe base material sheet, the base material is likely to flow into theconcave portion, thus suppressing the deformation stress that distortsthe pattern in the vertical direction. Therefore, the pattern distortionin this example was 0.08% that is an amount generated by the curing andshrinking of the base material.

Moreover, in this Example, the peel layer formed of an organic layer wasused. The peel layer is not necessarily limited thereto, and forexample, plating layer such as a Ni plating layer etc. having athickness of 200 nm or less may be used. In this case, the transfermaterial having the same effect was obtained.

Furthermore, the semiconductor chip 2608 was flip-chip mounted on thewiring 2613 easily by positioning the bumps with respect to the wiring2613 formed on the concave portion.

The mounting position of each of the circuit components (inductor,capacitor and resistor) was accurate. Thus, a precise circuit substrateas designed was produced in one transfer. The wiring substrate of thisExample was excellent in connection between the semiconductor chip 2608and the wiring 2613. Also, a capacitor 2606 that was mounted so that itfunctioned as a bypass capacitor functioned excellently. Furthermore,when capacitor high temperature load reliability test (125° C., 50V,1000 hours) was carried out, the insulating resistance of the dielectriclayer of the capacitor 2606 was not deteriorated and the 10⁶Ω or more ofinsulating resistance was secured.

Furthermore, the dielectric constant was 200 for the dielectric layer,and 8.1 for the substrate layer. An inductance of the inductor 2605 wassecured to be 0.5 μH or more, that is a sufficient value, even whetherit is ferrite or a magnetic alloy. Furthermore, the resistance value ofthe resistor 2607 could be a desired value ranging from 100Ω to 1 MΩ.

Thus, the use of the transfer material of the present inventionfacilitates the formation of circuit components including wiringpattern, active components such as a semiconductor chip, and passivecomponents such as an inductor, capacitor, and resistor, etc.

Example 14

With the fourth to sixth transfer materials of the present invention,and by using the substrate formed of composite material produced by thesame method as in Example 13, a multi-layered wiring substrate wasproduced as shown in FIG. 25. FIG. 26 is a cross sectional viewschematically showing the method for producing each layer.

As shown in FIG. 26, reference numerals 2800A, 2800B and 2800C denotetransfer materials, respectively. 2800A denotes a transfer material onwhich mainly a resistor 2803 is formed by printing. 2800B denotes atransfer material in which mainly a dielectric layer that serves as acapacitor 2804 is formed by printing. 2800C is transfer material inwhich mainly a magnetic layer that serves as the inductor 2805 wasformed by printing.

Furthermore, in this Example, as shown in FIGS. 26A to 26C, inner viaholes in the substrate sheet 2806 are filled with the conductive paste2807. Since the configuration of this was the same as in Example 13, thedetailed explanation is not repeated herein.

Furthermore, the wiring pattern layer 2808 formed on the surface of thetop layer of the multi-layered substrate and one electrode 2809 of thecapacitor 2804 were formed on the substrate previously. Moreover, thetransfer material to be used for the transfer has the same configurationof the transfer material of the present invention.

Conventionally, when passive components formed by printing areincorporated into a multi-layered substrate, an individual component wasformed by printing on the substrate green sheet. However, in such aprocess, the unevenness having a thickness of a several tens μm occurson the surface of the substrate. Therefore, if many layers are laminatedfor obtaining a multi-layered structure, when sintered and pressed, anexternal terminal of the outer capacitor etc. is deformed as squashed,thus deteriorating the insulating property. Thus, the short circuit ofthe capacitor was generated frequently.

In this Example, as shown in FIG. 26B, the electrode 2802 and thedielectric layer 2804 formed on the transfer material 2800B were pressedwith positioning onto the electrode patterns 2809 that were previouslyformed on the substrate sheet 2806. At this time, these electrode 2802and dielectric layer 2804 are embedded in the substrate sheet 2806having an excellent in fluidity. As shown in FIG. 26B′, a single layeredwiring substrate was produced without unevenness on the surface.

Similarly, when the transfer was carried out by using the transfermaterials 2800A and 2800C, no unevenness occur. As shown in FIGS. A′ andC′, a flat level was formed respectively.

Finally, the single layered wiring substrates shown in FIGS. 26A′ to26C′ and the wiring substrate to which the wiring patterns weretransferred on both surfaces as shown in FIG. 26D′ were laminated into asheet, and the sheet was cured in one heating and pressing treatment.Thereby, each layer in which the circuit component such as an inductor,capacitor, and resistor are integrated, thus a multi-layered circuitsubstrate as shown in FIG. 25 can be produced. In this example, eachlayer has a flat surface without unevenness, and thus a laminatingprocess can be carried out easily.

As mentioned above, the fourth to sixth transfer materials of thepresent invention allow a fine wiring pattern as well as circuitcomponents such as inductor, capacitor, and resistor etc. to be formedby a printing method and to be transferred in one transfer process.Therefore, easy and accurate mounting to the substrate can be possible.Furthermore, since the wiring pattern and component pattern are mountedby transfer, the wiring pattern and the component patterns can beembedded without occurring unevenness. This facilitates the subsequentlaminating process without disconnection of the wiring or damage of thepattern shape.

Moreover, in the fifth to twelfth embodiments and Examples 11 to 14, thetransfer material on which all of the inductor, capacitor, and resistorare formed is described, however, all of these components are notnecessarily formed.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The embodimentsdisclosed in this application are to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, all changes that come within the meaning and range ofequivalency of the claims are intended to be embraced therein.

1. A transfer material having a layer to be transferred to an substrate,the transfer material comprising: at least three layers of a first metallayer as a carrier, a second metal layer as a wiring pattern, and a peellayer that is provided between the first metal layer and the secondmetal layer and temporarily adheres the first metal layer to the secondmetal layer; and a circuit component that is formed on the first metallayer by a printing method for electrically connecting to the secondmetal layer, wherein the peel layer is a layer that temporarily adheresthe first metal layer to the second metal layer during a time periodfrom a time when the peel layer is formed on the first metal layer up toa time when the second metal layer and the circuit component aretransferred to the substrate.
 2. The transfer material according toclaim 1, wherein a thickness of the peel layer is 1 μm or less.
 3. Thetransfer material according to claim 1, wherein the peel layer is anorganic layer or a metal plating layer.
 4. The transfer materialaccording to claim 3, wherein the peel layer is an Au plating layer. 5.The transfer material according to claim 1, wherein an adhesive strengthbetween the first metal layer and the second metal layer via the peellayer is 10 N/m or more and 50 N/m or less.
 6. The transfer materialaccording to claim 1, wherein the circuit component comprises at leastone component selected from the group consisting of an inductor, acapacitor and a resistor.
 7. The transfer material according to claim 1,wherein the circuit component is formed of a material comprising aninorganic filler and a resin composition.
 8. The transfer materialaccording to claim 1, wherein the circuit component is formed of amaterial comprising an inorganic filler, an organic binder and aplasticizer.
 9. The transfer material according to claim 1, wherein athickness of the first metal layer is 4 to 100 μm, and a thickness ofthe second metal layer and the circuit component is 1 to 35 μm.
 10. Thetransfer material according to claim 1, wherein a convex and concaveportion is formed on the surface portion of the first metal layer, theconvex portion corresponds to the wiring pattern of the second metallayer, and an upper layer on the first metal layer is formed on theconvex portion.
 11. The transfer material according to claim 10, whereina height of the convex portion in the first metal layer is 1 to 12 μm.12. The transfer material according to claim 1, wherein each of thefirst metal layer and the second metal layer comprises at least onemetal selected from the group consisting of copper, aluminum, silver,and nickel.
 13. The transfer material according to claim 1, wherein thefirst metal layer and the second metal layer comprise the same metalcomponent.